Feels like Mueller must be really close to something at the top.

For the longest time, the Republicans acted not at all concerned with his investigation and basically dismissed it when asked. Trump said it was expected to end soon and he looked forward to being vindicated. Some even still praised Mueller as a qualified, trustworthy person to serve in his position.

Now, very suddenly, it seems like the Rs are coming at Mueller from any angle they can. I have to wonder what he's on the tail of, that they're so abruptly and simultaneously working to bring him down.

That said, I doubt they'll succeed. Mueller is highly respected, he knows his stuff, and he's surrounded himself with the best legal team he possibly can. They know whether they're in danger or not when they do something.