They need to solve the issue of speed, altough maybe for sensitive queries(assuming that's enough, a very big assumption,), people may be willing to use a slow "super private browsing mode". another option is to make people pay for faster speeds ?

And if i recall correctly, a "global passive attacker" listening to internet traffic around can de-anonimize TOR using ML. Seems like something that would be possible and profitable for a Google and internet infra companies.