[aerotwelve]

The pre-2015 net neutrality rules you're referring to were put in place in 2010 by the FCC under then-chairman Julius Genachowski.

https://en.wikipedia.org/wiki/FCC_Open_Internet_Order_2010

The key about the 2010 rules is that they did not reclassify ISPs. These rules were similar (actually much weaker) to the 2015 rules, but they were issued under the authority the FCC claimed to have over Title I services. As most here know, from 2005(ish?)-2015, cable/fiber ISPs were regulated under Title I.

ISPs sued and argued that since they were Title I services, the FCC's 2010 regulations were illegal. The judicial system agreed (Verizon v. FCC 2014). The solution to this problem -- the court explicitly told them this -- was to reclassify ISPs as Title II services; FCC would then have the proper legal authority to re-issue their NN regulations. Wheeler's FCC did this in 2015.