audio
the short version
in 2010 The FCC created a compromise rule to change rules that were in place from 2002, you can read about it here
https://en.wikipedia.org/wiki/FCC_Open_Internet_Order_2010 but essentially this was a rule that enforced a kind of flimsy net neutrality with a good deal of leeway for the ISP's but also named them Common Carriers which the ISP's didn't like.
so in 2014 Verizon sued, and won
https://en.wikipedia.org/wiki/Verizon_Communications_Inc._v._FCC_(2014)
which changed the rules again in 2015. The Obama admin responded by reclassifying. Ironically Verizon brought this on themselves when they had an OK Deal. From what I recall ATT, Comcast and other were annoyed at Verizon as the old deal was workable for them even if it was sorta crap for us.
that lead to this and it's why saying "We didn't have this before 2015" is both true at a very specific level and not true at all on a functional one. We had a version of Net Neutrality but not the same one we got in 2015 which was much better for consumers
Oh and we also developed deep packet inspection and have been able to effectively deploy it at scale making it more and more technology feasible for ISPs to actually implement their bad behavior.
https://en.wikipedia.org/wiki/Deep_packet_inspection