Why couldn't Jesus have intentionally acted in a manner that could/would be interpreted as fulfilling the prophecies? He was called "rabbi", so he must have been familiar with the scriptures; surely he knew the Old Testament prophecies and what he would need to do in order to be seen as the Messiah.
Well if he existed, then of course he might have acted in any way he wanted. But the question is did he exist. And the only way to answer that is with genuine credible evidence. But there is actually no evidence of his existence as a human person known to anyone at all at the time.
The evidence which does exist, is all evidence of religious belief. There's plenty of evidence of that. Evidence that the gospel writers (for example) believed he existed (in some sense of existence at least) ... but what they wrote in their gospels was evidence of their religious beliefs, not evidenec that any of them had ever known any human Jesus. And as Randel Helms and others have shown, that was a belief they were certainly obtaining from reading messiah prophecies in their old testament.
If people here want to believe, as many have in fact stated, that they think it more likely that the gospels and letters would have been written about a real person (Jesus), then that is a matter for them. But in that case they are not basing their HJ belief on actual evidence of his existence. On the contrary, the evidence which is being used, i.e. the gospels and letters of the bible (which is the only source of evidence for Jesus), is evidence which is actually very strongly against that biblical messiah being a real person.