One thing I remember in reference to Loki's intelligence is, when talking about the original myths, he's not particularly, like... smart. His idea of "trickery" is just "blatantly lying and getting away with it." Like, with Idunn, the keeper of the golden apples of immortality, he just tells her... hey, I found some even better apples out in the woods, let's go check 'em out. And it works! Loki isn't smart, he's just charismatic and morally flexible and lucky to live in a society with lots of easy marks.
The original Thor movie is him playing a role - he's the "good son," keeps his head down, works hard, "deserves" power. It's the only time he's really truly ambitious with his scheming, and you can imagine he's had centuries to think about it. After that point? He's mostly just winging it, coasting along on second chances from Thor and some parlor tricks.
Here, as in Ragnarok, we're not supposed to take Loki seriously. He's a joke at this point - he had a couple big shots at victory, he bombed twice, and now he's just playing the greatest hits to a dwindling crowd. The whole first episode, from the dismissive TVA to his pitiful post-Avengers life, is a wakeup call that he's an arrogant, talentless loser who only made it so far thanks to good luck and a family that gives way too many chances.
