Some it was probably "this gives us an excuse to rewrite the system, but better this time!" Rebranding often gives a certain amount of cover to do things you want to do even if you don't have to do it.

Often new management wants to put their stamp on things. I've been in situations where we've had to do major redesigns because a new leader wanted to leave their mark. I've been in situations where each new leader wanted a new logo to mark that they made a difference - 3 logos in a decade.

Companies often squander resources in this kind of way. That's not to say that some redesigns and changes aren't warranted, but these things happen often. Why has Google launched a dozen chat apps? Why do some apps get a huge push followed by being abandoned followed by a huge rebranding/recoding push followed by being abandoned again? Many people on here have speculated it's because people get promoted for launching big new things and not for things that seem "easy" like maintenance.

You're rightly baffled from a logical standpoint. When you start thinking about the humans involved in the situation, their egos, their priorities for themselves which might not align with the company's, etc., then it potentially starts to make more sense.