3) Removing "unnecessary cruft" during the rewrite, measuring the speedup and then gradually adding the "cruft" (features) back one by one as previously unknown boundary conditions are encountered.
Restart the process again after a few years of years, as is tradition.
This is not what happened in this case (although I have seen this pattern in other situations in the past). The Rust version is a faithful port of the feature set of the Python version. (It had to be, we were using essentially the entire feature set in production.)
This effect is the reason my default is to be skeptical of benchmarks of new software. It's easy to be fast if you're willing to be incorrect or incomplete.
Restart the process again after a few years of years, as is tradition.