In TLJ we already saw Leia herself was preparing Poe to assume a role of leadership, that was his whole character arc in the movie and it ends with him assuming command of the remaining Resistance members, “What are you looking at me for? Follow him”. It’s true this movie regresses him into hotshot pilot mode, but from his irritable attitude and his convo with Zorii at least there’s a sense that he’s overwhelmed by the responsibility, and he’s been putting it off because he thinks he’s not ready. It’s only after Leia dies that he feels like he has to step up and assume the role she wanted for him.

At least that’s the way I look at it, and it’s stronger if it’s something Poe chooses to do, rather than being told he has to because it was Leia’s dying wish. It was the expected progression of his character coming from TLJ, yeah he probably should’ve started the movie as more of a leader, but like most characters in the sequel trilogy he falters before stepping up and doing the right thing.