Besides this the reasons for regulation are pretty damn compelling. Clear cut case of market failure. You cannot take your business elsewhere to deal with the failings of big tech. It is an industry with a long run decreasing average total cost curve and has network externalities. (Hence why there aren't 27 similar magnitude businesses competing in the Facebook space, for example).That's not market failure, it's normal market functioning today. It used to be that the limits of scaling kept companies in most industries from becoming monopolies. The industries with really strong network effects, railroads, communications, and banking, were highly regulated.
Now, more industries have strong network effects. The negative effects of scale, big companies unable to get out of their own way, seem to have been conquered. Planetary-scale companies such as Walmart and McDonalds work quite well, and they're not even "tech" companies. And US antitrust enforcement has been out to lunch for 30 years now.
The European Union has a study, which I've cited before, that price competition seems to require, in practice, at least four major players. There's an implicit collusion effect that makes it more profitable to not compete on price where the number of players is small.