Because they 're two of the stupidest jacksses ever born. They'll fall all over each other while they out stupid the other one. They have no concept of anything beyond their own assholes. It doesn't dawn on them, that if they ruin Williams place in the Monarchy, there will be no Monarchy for them to trample? Their best bet, is supporting William's destiny. But, again, they're too stupid to see that.
I think that H, on his own, would never have gone beyond his whiney, self-absorbed catalogue of complaints - it’s not fair, William got this, m’pater did that… But TW took his pathetic peeves way beyond the purely personal into far more damaging territory, eg, Will’s kids automatically getting royal titles, unlike the spare’s kids, became a thing about kids with darker skins not getting royal titles and so ‘racism’ in the royal family.
You do have to wonder what goes on in H’s tiny brain as he sees his peevish utterances being spun into damaging allegations against his family, the monarchy, and the British public.
(Answer: Not a lot.)