I think part of the reason Segwit2x failed is that, ultimately, mining wasn't as centralized as everyone assumed. Its proponents had the backing of the major mining pools who controlled the vast majority of the mining power - or so they thought - but it turned out enough of the actual miners had views too and were happy to switch pools to express them that it suddenly looked a lot more precarious than expected.
Controlled by a handful of people is absolutely not decentralized.
They have abused their power. Ghash double spends. Segwit blocked for a year. Bitcoin cash proxy support.