Nobody has validated the Fediverse as a place to make money.
Sure, tiny web-hosts might charge for services, but the average Big Social executive isn't looking to make tiny increases in a new venture. They want to 100x or 1,000x their ROI.
Somebody might eventually try this, but Big Social isn't going to be first.
Yes, Big Social has more than enough money and tech to upset the Fediverse.
What they don't have is the capacity to onboard knowledge about the Fediverse quickly and easily.
This is because the actual inner workings of the Fediverse are held by only a small handful of people.