This is like my take on this too. Waiting until after the election is a big indicator. He's not doing this to show that he is a serious AG. He is doing this to improve his image as a governor. This has nothing to do with getting rid of election fraud.
No, a sitting President cannot be arrested and indicted. We don't want the government itself to have power over the elected politicians. This is the biggest lesson from the Trump administration. The Constitution clearly states how a President is removed from office, and it has nothing to do with the DOJ.