This is just a little musing for now.
Isn’t there an inherent problem with public prosecutors, in that prosecuting crime is supposedly an executive branch prerogative, whereas (as officers of the court) a prosecutor is an official of the judicial branch?
In other words, how can you maintain the separation of powers in a situation where one official – the public prosecutor – belongs both to the executive branch and the judicial branch?
It would seem better, from this standpoint, to have criminal prosecutions conducted by private attorneys who are not members of the executive branch. Indeed this was common practice in the United States through much of the 19th century.
On the other hand, it would also be important that the private attorney prosecutor not become confused about who he represents: if he thought of himself as representing the “victim”, that might be a conflict of interest and could wind up being a due process issue for the targeted defendant.
I realize this seems to be one of those big ideas that aren’t relevant to anything useful, but appearances can be deceiving: we have a very dysfunctional system and fundamental changes should be on the table. Otherwise we are just tinkering.

And while we are at it, let’s eliminate the vice-presidency, as well. Let someone run for a six year term to be President of the Senate.
And furthering your point, is it any less surprising that so many state prosecutors aspire to and end up on the bench?
From a separation of powers point of view, it is disturbing. More so because it is so common.
Once in a while I tend towards understatement.