ASICBoost, the reason why Bitmain blocked Segwit.
TLDR; Bitmain wanted to push Segwit either through a hard fork, or in Extension Blocks which would be compatible with their ASICBoost. A soft fork of Segwit, which is by far the safest option, isn’t compatible and they would lose their advantage over other miners.
https://medium.com/@WhalePanda/asicboos ... 1fd346ee9f