OPINION START
The "left" has a lot of infighting between each other because people don't really know how to implement their worldview. So that already prevents tribalism across the entirety of the "left".
The "right" is much more tribalistic, so it's easier to feel like you're part of a group in the far right. The only thing you need to do is hate the "left" and everything they stand for.
It's easy to blame a group of people for your problems, it's harder to design a society that can include everyone without having those problems.
This then makes the "right" much more united.