The first half of this story made me wonder if we were colleagues.

The second half was different though. Our guy was a personal friend of some high up, slandered the existing codebase without so much as even speaking to the existing devteam, and then took the better part of a year claiming he could replace the entire decade old codebase while making vague promises that it was coming soon. Meanwhile upper management was taking the slander seriously, punished my department and got a new manager for it. It wasnt until the new manager outed him as a fraud for his ass to finally get caught.

I doubt he was able to read the legacy codebase at all.