This is not a centralizing pattern, because there are different drivers for attention and engagement.

Some want "the sure thing" (i.e. proven content, that others liked or engaged with). Enterntainment, news, etc.

But others want "new and interesting takes" (i.e. from undiscovered accounts with very good points). They're usually discovered when they give an insightful reply. They also have typically very few followers. Their follows are of a similar kind, so if you wnt to follow more "new and interestin takes", such "low profile' accounts are loosely inter-connected. That's why on Bitcoin Tiwtter, some of the best takes come from frog and cat profiles.

So IMO there are competing drivers that spread engagement out across a network.

Besides, once an account gets big, their voice and style changes. They have more to lose, so they tend to cater to their audience. They lose their edge, which part of their audience now switching to contenders in the space.