From Cory Doctorow:

Here is how platforms die: First, they are good to their users; then they abuse their users to make things better for their business customers; finally, they abuse those business customers to claw back all the value for themselves. Then, they die.

https://www.wired.com/story/tiktok-platforms-cory-doctorow/

Some of it is because we had a decade of cheap borrowing which has come to an end and many of these platforms were never profitable.