Sorry if it sounds too cynical, but that's probably the intended effect of a rewrite from what the team knows into Python: staffing changes. A bunch of the (expensive) old guard will leave and they can be replaced with cheap grads, who all know Python.

Better luck with the next one!

If that is the case, it's a good thing. I'm stuck in a big dept using C++ for very high-level stuff that anyone else would absolutely not use it for.

I've probed several times, and the most senior SWEs have no reason for this choice other than some personal issue with anything new, which to me sounds like a job security thing. Over time, they've resisted other new tooling to the point where management has ended up forcing things, but they're still holding onto C++. Some lower-grade, lower-ego engineers armed with higher-level tools would replace everything in a more maintainable way for a lot less money.