Some Republicans (enough to have an effect) are mean-spirited. Heck, they ousted McCarthy simply because he negotiated a deal with Democrats. They actually said there should be no negotiation, but he did it, and they ousted him for it.

There may be a contingent of Dems of similar attitude, but they are small and ineffectual. The Reps' contingent is vocal and has a lot of influence.

Are they in love with Russia? I think many don't care. Effectively, modern isolationists. They don't care about Ukraine, NATO, Europe...none of it. Echoes of the 30s when people like Lindburgh were saying that Europe's problems weren't our problems (he was one of the more prominent and influential people of that time). Others (the more gullible) think that if Trump is OK with Russia, then they're OK with Russia. After all, Trump said a lot of nice things about Putin, so he must be OK. Right?

I don't actually view the Reps as monolithic. But when they enact (or block) policy, it's a convenient shorthand to say "Reps did this", because they did, even if not all Reps agreed with it.