That's not a failsafe. The whole point of a failsafe is to override a system in case it fails. 51% wrong or malicious consensus IS system failure in Bitcoin; a "failsafe" would be something that can override that.

The only "failsafe" you can argue Bitcoin to have is that in such an event, the developers can hard patch a malicious user or users out of the blockchain, or users can fork the blockchain.

But guess what: you don't know that 51% user or users are malicious. How do you know it's not the ulterior motive of a minority to pretend that they are? You don't know. Also, unless you are extremely ignorant in how politics works, it is in fact incredibly easy to make a centralised 51% attack. Go see the last American presidency if you want an example of that.