Never mind, some people hate Uijtdebroeks just because he had the audacity to leave Bora. Everyone else knows he's just a nice guy with a lot of enthusiasm for the sport who doesn't deserve to be struggling like he is now. Clearly something is physically wrong and they have to find out what it is. He's not just stalled, he's regressed massively and that's not normal for a guy barely in his twenties.
In sport it's actually really normal. More normal than you might think.
Forget Bora or whatever other 'deep' reason you seem to assign his 'haters' (aka an emotional negative label which doesn't exactly reflect the tenor of the conversation here) and what we're left with is a borderline stereotypical case of a young athlete who broke through early in the sport and is struggling to live up to the expectations he had of himself. Nothing more.
It happens in cycling, tennis, football, you name it. And what Uijtdebroeks is experiencing might not uniquely be seen as a 'regression', i.e. it could also be seen as a form of plateauing whereby the level he was at 2 years ago isn't so far removed from his current level (he did finish 5th in the recent Tour of Oman, FWIW, whereas he was 9th in the same race with Bora in 2023).
He simply isn't making the gains he wanted or expected at Visma and that could be eating away at him mentally. So when the racing gets tough, boom, he explodes in his head.
We've seen it all before.