The far right loves a strong man, and by definition there can be only one of those, prefers when “the natural order” is followed, and thinks the ends always justify the means. That keeps them pretty cohesive with the establishment right, who are making buckets of money under the system as it is now and are okay with just about anything else as long as that doesn’t change. When they fight, it’s because the far right is trying to do something stupid enough that the establishment thinks it risks their money or power, or the establishment is holding the far right back from fully implementing their “natural order” worldview, but there’s a lot of overlap where both can be happy, because the establishment really has no morals at all and are happy to use the far right to gain power if all they have to do is throw them some red meat every once in a while.

The left’s a very different story. On the far left, people are very principled, to the point where compromise or partial wins feel hollow because the only real win would be the entire principle being adopted en masse. It makes it harder to work together, because even groups with the same goals can get frustrated by the way the other one is doing it, or because the other group is going to keep going while the other wants to stop sooner. And the establishment left has a fair amount in common with the establishment right, they find the right’s goals uncouth and mean, but they do still fundamentally believe in capitalism and don’t want to upend the system. That leaves a lot less common ground and a lot more infighting overall.