Politics and the need to have the Core developers out. Some say it was because it would render Bitmain's Asic boost useless, and all other reasons that distracted us away from the truth. But I believe it was politics.
I will leave Achow and the rest more learned about the situation to comment.
People would say a lot many things about it but so far what I have learned about segwit2x it is just going to promote the use of bitcoin by reducing the transaction size, time and fees. But half of the world was against it because they actually did not know about it properly. In this crypto world people very quickly just follow the steps of the top members of community rather than using their own brains. Like if one of the core miner would say its not good around 5% of the community would declare this to be not good. Same happened with this too. Miners gave their support to this venture in beginning and snatched that as we moved closer to that block because they knew it would burn a hole in their own pocket by reducing the fees. People blindly just followed the pattern and here we are today still using the same old pattern by faying a lot hefty fees.