I think there's some merit to the idea that huge corporate monopolies have the resources to accomplish undertakings that smaller companies cannot. But it's often a what-if, because we don't know what the alternative might have been.

Big companies can suck up all the air in the room by monopolizing talent and making it harder for startups to pay the kinds of salaries needed for top tier AI research. Xerox PARC came up with all kinds of groundbreaking inventions that were never commercialized (by them). For every invention that comes out of a big company, it's worth thinking about whether it might have actually come out faster if it was borne of competition instead of a side project. Or in the grand scheme of things, if corporate taxes were higher and the money was given to a university research lab.

I think the best results may come from the middle ground. Smaller/medium companies are so worried about staying afloat or hitting their quarterly earnings that they have trouble making long term investments. Large companies are diverse and profitable enough that they can afford to blow money on things that might not pan out, but they don't have the same drive -- and in fact have some pressure to avoid being "too" innovative because it could cannibalize their existing products.