The answer is yes, and no.
Yes, because it is consistent with Light's character earlier in the series. We see when he feels pressured or boxed in he lashes out (like when he kills Kind L. Taylor) or has a lapse in composure (like when L reveals himself to him).
So, viewed from this angle, it's perfectly consistent with his character to act the way. The trouble is that the Light of the finale isn't the Light from the start of the series. Even midway through we see his behavior changing, as he learns to handle these tight situations. For example, when he expects Rem to kill L or Misa to see his name with her shinigami eyes, L sidesteps the situation and takes Misa into custody, not only destroying Light's plans and putting himself further in L's crosshairs, but he also ends up in Rem's crosshairs, too, as she threatens to kill Light should anything happen to Misa.
But even with the pressure coming in from two sides, Light doesn't panic, but instead quickly formulates a plan that allows him to ultimately come out victorious over both L and Rem. Light is also a good bullshitter, and is able to string people along fairly well, even while they're suspicious of him. If he hasn't lost his cool, he could probably have kept talking just long enough to subtly write down Near's name in the Death Note, which would possibly allow him to escape in the brief moment if confusion and chaos when Near dies. Even in the actual ending, Near is momentarily concerned that Light has something up his sleeve when he poses the question about which Death Notes are the real ones. I think that if he acted less rashly he could have planted enough doubt (at least in the mind of the Task Force) to buy himself time to pull out a Hail Mary, which would have been moee consistent with the quick thinking Light who defeated L.
We also have to remember that Light of the finale is 23 years old, and not the 17 year old kid who only had the Death Note for weeks or months when he acted rashly in those earlier instances. Of course, the counter argument is that Light simply got too arrogant and got sloppy over time, or that he simply reverted back to a more childish state upon being outwitted, but the trouble with these arguments is they don't make as satisfying an ending. I mean, when you can accurately sum it up as "Light got dumber, then lost", it doesn't feel like a very grand conclusion to what came before.
This is really just the fault of the last part of Death Note being sloppier than what came before though. Another example of this is how it sets up the idea that we'll be seeing a three way battle between Light, Near, and Mello, with each side out to get the other two. Mello in particular seems like he'll be an interesting character, because while he wishes to surpass L and catch Kira, he has no issue attack Near and harming or killing innocent people to get his way. He lacks both the morality and sense of justice of both Kira or L, which means be could be potentially both better or worse than Light depending on the scenario.
What we get initially is a pretty bad guy who's more of a threat to both parties than either are to each other. He works for canonically the most evil character in the series (Rod Ross) simply because it benefits him to do so, he kidnaps and traumatizes an innocent civilian (Light's sister Sayu) in order to threaten her life to force Light to hand over the Death Note (which he does, meaning if anything Light's family is probably his biggest weakness, even over any arrogance), and then once he gets a hold of the Death Note he uses it to kill all if Near's team. In the manga he goes even further, causing the president to commit suicide when he threatens to control him with the Death Note in order to start a nuclear war, in order to try to blackmail him into giving him all the info on Near (who was being sponsored by the United States). And then after all this, he kills Light's dad in a rash bombing which scars himself in the process when they try to retake the Death Note back.
So wow, this Mello character is pretty crazy. He's probably more dangerous than Kira, since he wants to win at all costs, everything else be damned. I can't wait to see what happens to him! Wait, what do you mean he disappears for the rest of the series until he shows up right before the end so he can die in order for Near to win, just so we can have a less interesting rehash of L vs. Light with Near as an L stand-in?
Anyway, my point is that yeah, the second half of the series is just not as well plotted out or written than what comes before. A lot of the inconsistencies one may have with Light (or any other character) by the end can partially be chalked up to that.
Lastly, I'd like to dispel this notion that Light wasn't as smart as he thought he was. Light is ranked by the author of Death Note as being 10/10 in emotional strength, social skills, and creativity, and has a 9/10 in knowledge. L in comparison has 1/10 in social skills, 10/10 in emotional strength and creativity, but only a 8/10 in knowledge. The only area L beats Light is in initiative, where he has a 9/10 in contrast to Light's 8/10.
If anything, they're very evenly matched, but Light's superior social skills and greater knowledge probably put him out on top more often than not. L is definitely more experienced than Light, but Light probably had the potential to surpass him, which, I think if you consider he defeated him, he did. (And yeah, yeah, "But Light had unfair advantages, like the Death Note and Rem!", yes, but L had unfair advantages like unlimited finances and authority and a name that was near impossible to learn, so it's a wash.)
Plus, the author even stated that if Light never picked up the Death Note he would have gone on to become one of the greatest police leaders in the world, and would have eventually worked with L, so like... It's hard to argue he wasn't as smart as he thought. If anything, he was arrogant because he was as smart as he thought. Not the other way around.
Anyway, tl;dr: Light's behavior at the end is fairly consistent with his early characterization, but more inconsistent with his behavior and levelheadedness displayed later on. This change in behavior is probably due to less than stellar writing, but you can handwave it as saying he got too arrogant or lazy, or whatever you need to to make to work, even if canonically he's still supposed to be super, super smart. Except in the live action TV drama. That version of Light is definitely a normal dude who gets outsmarted by L every which way so bad that it's pretty sad in the end.
