I think that can often be a problem in political structures, but I don't think this is the main issue. It might explain how their messaging is so terrible, but the republicans have clearly managed just fine and the average is almost exactly the same in both.
I think it's primarily that they see support for Israel as an absolute necessity because it would (1) be another massive loss of support and political funding, and (2) a very difficult pill to swallow. Admitting to having supported a horrible genocide in full conscience and trying to convince that they have now learned their way might still look like a steeper hill to climb than the time-tested tradition of genocide denial.
It'd be great if it was the main issue though, I think you're right in that at least they would have better messaging, unfortunately I don't think the actual policies would be much different. In Europe for example fascist parties tend to be pretty young 🤷♂️
Yeah I thought this was too big aswell, but you can just go on truth social, his post is still there.