I know you don't get it. Most people don't. And no, you're not a smart as you think you are.
The fact is the GOP Establishment (Washington DC) is in alignment with Democrats with mutual (but differing in other areas) interests. In effect, it's Trump vs. the World at the political and geo-political level. So here comes Trump, trolled the entire process, and WON election. Shell-shocked the fuck of the entire political echo chamber. I mean, how could "the pussy grabber" win?? Easy. Real real easy! He wasn't a conservative. This wasn't an election about values. It was an election about justice. It was rural vs urban. And, it's being played out all over the world. It's how the Brexit happened. It's how the world is pivoting away from Globalism due to the stratification of wealth it has caused, eviscerating the middle-class in the process.
Ok, so again your asking "why Mueller?". Notice all the others that smell opportunity after a Trump victory? Mark Zuckerberg, Jeff Bezos (maybe), Kid Rock, Dwayne Johnson - AKA The Rock...all of them are OUTSIDERS. Even to a lesser extent, Bernie Sanders was an outsider to the DNC. In fact, the Deep State FBI is going after his wife. Never mind the fact the Clintons have entire cemeteries while Jane had few skeletons in the closet. The DC establishment has a few fires to put out, and they will punish and stamp out anyone who's not them. They will not let that insolence to their way of life stand!