Especially at the national level, most politicians hire staffers they trust to implement their policies in accordance with their principals, and harshly punish those that won't. The closest advisors tend to be either referred from their state party, or people that have risen through the ranks with them, so they're often decades old relationships, or at least people that have been in the same circles for years.

The day to day does involve a lot of reading, meeting with lobbyists for specific issues (this includes a lot of non-money players, fwiw), and only rarely in depth policy discussion with advisors/other policy makers. They have to trust their staffers to highlight things they should hammer home/object to in legislation, and, because sometimes bills arrive in Congress already too complicated, they're sometimes unable to actually read the whole thing before voting (even in a "you take 200 pages, you take 200 pages..." sense), so they're essentially trusting that other people have reviewed it well enough.

It's a job with long hours, but a lot of that is essentially socializing, so not "hard" in the same sense as digging holes or whatnot is hard.