If 2x does somehow succeed, then most Bitcoin Core developers will quit Bitcoin entirely as 2x's success would mean that [...] companies can have absolute control over what Bitcoin does. [...]
To be fair, it is the bitcoin related companies that ultimately give Bitcoin utility (value), and whose opinions ultimately determine if any HF will be successful or not.
It should also be noted that it is the bitcoin related companies that have the most (really all) skin in the game in seeing that Bitcoin is ultimately successful.
I would also point out that if the core devs (that work for Blockstream) stop their development work on Bitcoin, then others will step in. The bitcoin related companies already actively employ many devs who could easily take over.