The FCC really started pushing for net neutrality in the Bush administration.
In 2005, the Madison River Telephone company (now Lumen/CenturyLink) blocked Vonage from using its networks and the FCC stepped in to stop them. They then established 4 principles of an Open Internet:
Consumers deserve access to the lawful Internet content of their choice.
Consumers should be allowed to run applications and use services of their choice, subject to the needs of law enforcement
Consumers should be able to connect their choice of legal devices that do not harm the network.
Consumers deserve to choose their network providers, application and service providers, and content providers of choice.
In 2009, they overtly added the principle of non-discrimination, and in 2010 they made the principles official with the Open Internet Order.
Comcast sued and got the order thrown out, so they started the prices of reclassifying broadband, and the fight reached fever pitch in 2014 when it looked like the FCC was finally going to win for us.
But between 2012 and 2016, the ISPs changed their tactics. They stated colluding with the major tech and streaming services pitching net neutrality as a good thing for the established businesses that could pay the ransom or engage in partnerships. A good example was T-Mobile exempting Netflix from their 2gig data limit on cellular plans. T-Mobile was able to advertise the partnership as a good thing instead of an assault on users and the open internet.
Then the Trump administration took over and took a huge steaming dump on the FCC along with everything else, and the Biden administration just spent the better part of 4 years just trying to seat a commissioner to reinstate open internet.