It's likely both, but i'd also argue that the lack of leadership could also be caused by increasing adoption. If many of the leaders left because the fights got too contentious, we need to understand that the fights get more contentious when there's more at stake, and when there's more adoption there's more at stake.

Bitcoin is already one of the world's largest asset classes. In some sense, it needs to ossify so that all the people and organizations with stakes riding on it have some degree of predictability.

I think we're at the point where L1 development is gonna become stale, for all the reasons stated in the OP, and most of the development will come from L2 products.