If the software is fast as a byproduct of being simple, that tends to align with correctness.
If it is fast because it is optimized, then that does not align with correctness, because optimizing something that works only adds risk.
Simple software is also easier to optimize. The simpler it is, the less weird corner cases you have to deal with.
Simple software is also easier to optimize. The simpler it is, the less weird corner cases you have to deal with.