Securing core resources has been a long standing national security concern for countries. Also, there’s a good chunk of populist isolationist sentiment in the zeitgeist.

Senators aren’t unbiased. They’re biased towards what their voters want. If they step out of line, they’ll likely get crushed.

I don’t think money in politics is very explanatory. It seems a basic understanding of the 3 branches and the interplay between the states and federal government explains a lot.