I think the tipping point was in the early 2010s when all of a sudden everyone and everything hitched their wagons to Facebook. Facebook as SSO, Facebook messenger instead of email or SMS, Facebook marketplace dethroning Craig’s List, etc. Once people from elderly relatives to local business centralized all of their online identity into Facebook, it was over. To this day, Facebook is still the only way to see info for community events and small businesses (and instagram is the platform Facebook used to sequester musicians and artists).
It didn’t have to be Facebook, of course, but there needed to be a networked service that people trusted enough to give it every thing. Remember check-ins? People would post their location at restaurants, jobs, theaters, and shops. Public profiles that listed jobs, homes, family members and relationships, pets, children’s photos, and hobbies all under real names (I remember when Facebook started the purge of pseudonyms and aliases).
I deleted my Facebook account over a decade ago and people panicked and warned me that it was a bad idea. The craziest thing someone said to me was that it would make me un-hire-able since there’d be nothing for people to snoop to see if I was a good fit. The only “bad” thing that happened is that I lost contact with some old acquaintances, but that’s just life.
Regardless of all the other tech stuff in the past 20 years, I think that convincing people that it was okay to let a company like Facebook exist will the explicit goal to transparently harvest personal data was what opened the floodgates. Facebook (and other social media) demonstrated that people will willingly exchange privacy for digital errata. Once governments and corporations saw that, the future wrote itself.