Have there been any so brazen as Musk, who used his influence to infiltrate our government and usurp the congressional power of the purse directly and illegally?

Details are different, but there have been lots of examples over the years. Andrew Jackson had his "kitchen cabinet". There was https://en.wikipedia.org/wiki/Teapot_Dome_scandal, Watergate. There are plenty of other examples. In large part if something is an example or not depends on your politics - people tend to overlook the mistakes of someone they support.