Based on similar things I’ve seen here in Australian political circles it’s because they are so deeply misinformed that it’s become dogmatic. They like to get simplistic overview briefings and dislike getting sufficiently deep briefings that they can be informed of the fundamental flaws that simplistic briefings pass over.

They also decide who works for them so no subordinate will “make them learn” and everyone perpetuates a cycle of ignorance that leads to the establishment of a dogmatic position that people trying to make things seem more complicated are wrong because I have all my own people telling me it’s not that complicated. Unless they care to be informed and ASK for it, it will never happen.

I have no evidence for this, but I think it's highly likely they're using "ignorance" as a form of brinkmanship or plausible deniability. If these senators speak with any of their colleagues, they'll know the risk and reward tradeoffs of these decisions, but they'll choose to side with interests that benefit their own person.

I know Hanlon's razor stands against me, but I just find the dynamics of a highly connected set of professionals in DC too conducive to passive knowledge of these issues to justify a bunch of "key senators" to be fully ignorant on these subjects. I find it way more likely that ignorance is a convenient narrative to push their agenda without accountability from the opposition.

Plausible deniability yes, but even just safety. If I don't engage with a topic in a detailed manner, it's very unlikely I'll say something wrong about it, that could later come back to haunt me. Remember "the internet is a series of tubes"? The guy was hammered for trying to understand a complex topic - and he wasn't even dramatically wrong, just used a metaphor (almost certainly thought-up by someone in his staff) that was just excessively reductionist.

The media playing gotcha has made it fundamentally dangerous for a politician to be publicly wrong on any topic. The reaction is to avoid engaging with complex issues.

idiocracy was a documentary

Thanks. Lots of commending! They must be a commendable lot.