They did and do support version control etc. E.g. even Smalltalk back in the day kept a log of every single change of code in what's called a "changes" file.

"Corrupting the VM" just means that you were editing the stack frame class in the live system running on the VM and as soon as you hit "save", the VM crashes. So you simply run it again. And if needed, replay the changes log up to before the crashing change.

This only takes seconds, and is part of the reason why Smalltalk is so productive.