Yeah, Chrom takes the focus in the first half of the game, which is similar to, say, Lyn's involvement in FE7. But it's just endlessly funny that after that intro it's the Robin and Lucina show and it's clear those two were the more popular characters.
I wouldn't really compare it to Lyn's involvement, though. Her arc is essentially a side story with a small scope, whereas Chrom's stuff kicks off the entire story and segues into the finale. It's not even Lucina's show after she joins either, because she ends up being relegated to a tertiary character with small bits of relevance here and there (first intervention / Basilio's death, etc) but nothing too significant. Honestly, I think you're experiencing a bit of source amnesia. The game is entirely about Chrom's relationship with Robin. They constantly beat over your head that they're two halves of the same whole. Their dynamic drives literally every scene (Robin is the rational one, Chrom is the emotional one, etc.)
The final arc is pretty much entirely about Chrom and Robin's relationship, culminating in Robin's "sacrifice" and Chrom's reaction to that. The "Chrom is a third wheel in his own game" is something that started a few years after Awakening, and something I bought into before I actually replayed the games.
Don't take my fascination with Chrom being seen as essentially a third wheel in his own game to fans as a sign that I don't like him as a character. He's fun and his dynamic with Robin and Lucina is good, especially when he feels bad that Lucina had to live in a future where he failed. But I just genuinely like that IS is aware of his dorkier nature (which honestly might be a nod towards Marth being kind of a dweeb compared to his supporting cast) and delights at people like sakurai "picking on him". It truly enhances his character, at least in my eyes.
Playing through Awakening is surreal because it was clear they tried to initially make him the straight man to everyone else's goofy bullshit, instead of the dork we know and love. But Sakurai's smash trailer was a game changer for him (Sakurai is incidentally, the reason why Robin became his own character after Awakening, imo).
Also, while I really like Ike, he's a total stick in the mud in RD, worse than in PoR. He's actually kinda dumb and naive in fun ways in PoR, but in RD it feels like he's too stoic for his own good.
RD Ike is the perfect culmination of PoR Ike's character development, though. His growth is legitimately one of the best aspects of that game, and he becomes a true leader in the sense that he doesn't use bullshit charisma to convince people, but measured words and confidence that come from experience.
Like I love how every idiot Lord waxes poetically about how war is bad, and how friends shouldn't fight and all that other bullshit when confronting a former ally, while Ike is just like:
Ike: Sothe, before you challenge me, you better be ready never to see that girl again. Can you handle that?
Sothe: Wh-what?!
Ike: If you can't, stay away from me. You'll get no mercy, despite our past. I'm sorry, Sothe, but the choices we've made have brought us to this. There's no turning back now.
No fucks. No saccharine waxing about how friends shouldn't fight. If you challenge me on the battlefield, you will die.
God, they never could quite get a good FE lord after Ike.