I suspect some of them don't want to admit that they were wrong and so they are putting on the blinders and sticking to their narrative.
I suspect some of them really are so incapable of questioning what they are told that they just can't believe anything else.
I suspect some of them are scared of what will happen to them if they don't carry the line.
I suspect some of them think that Trump will reward them for their loyalty.
I believe all of them are going to regret it.
I remember reading about the former tribal situation in Papua New Guinea in one of the Jared Diamond books. The country used to contain perhaps thousands of tribes, each one living within their territory of a few square miles and having almost no contact with others. If someone encountered a member of a different tribe, the reflex response was to try to kill them for being different. Sadly, humans seem to have this instinct in them, which we have mainly managed to overcome through socialisation and empirical experience. I think that instinct is still quite strong in many Republicans and supporters of far-right parties in other countries, which explains the racism, homophobia, and xenophobia.
Edit: I've thought a bit more about this, and the tribe analogy seems to nicely explain many of the Republican policies and the mindset.
1) The gutting of overseas aid: We shouldn't be helping other tribes.
2) Tariffs: If we must trade with other tribes, we must get what we can from them.
3) The pro-natal movement: We must make our tribe as big as possible.
4) Anti-abortion: Similar.
5) Homophobia/transphobia: Those people are not going to make our tribe as big as possible, so they are a waste of resources.
6) Abandoning of DEI: We should not help people who don't look like they are part of our (white) tribe.
7) Militant Christianity: Only our tribe's God is the true god.
Ideally, people with such views would keep themselves to themselves and not bother the civilised world, who understand reciprocity and value diversity, as the ones in Papua New Guinea did. However, having bright, shiny things, like smartphones, involves contact with the wider world. Hence,
8) We must appropriate resources from other tribes (Greenland, Canada, Ukraine).