Yeah, it’s the same thing as government issued currency the moment you put it in paper. A corollary is that digital dollars on your banking app is just like crypto.
Also, it can. See the Ethereum fork and Bitcoin Segwit.
Plenty of times the market value of Bitcoin has dropped drastically because one person said or did something.
If any developers tried to convince anyone to run Bitcoin software that debased their savings, they are going to have a very bad time.
I was a part of the bitcointalk forums in 2010 when the dev team created a soft fork that modified the blockchain to change consensus rules. THink about it, devs changed the consensus mechanism, that goes against everything bitcoin is supposed to be. They can do it again