> I haven't looked into the case(s) for years, but prosecutors don't often just drop charges because other charges were found guilty.

They absolutely do that all the freaking time. Especially when other convictions already result in a long sentence.

Prosecutors have limited bandwidth, and just wasting time adding one more life imprisonment on top of a life imprisonment is not helpful.

Perhaps. I can't think of why they ultimately decided not to move forward with it, but here we are.