Lol Credibility!
Do you think Trump believes in stupid ideas like "Credibility"? Or do you think those who vote for him do so because of "Credibility"? I mean this is Trump we are talking about! The Pussy Grabbing, Russian Golden-Showering, Disinfectant Injecting, Pandemic Denying Trump! The guy literally said "I don't take any responsibility"!
No dear, his cries of Fraud are indeed losers cries but it will work like magic with his base! People always identify with a fighting losers specially the loser who was beaten by "fraud". He is making a martyr out of himself for his base. The guy who was beaten down by smooth talking politically correct college educated liberals. Nothing makes him dearer to his base than these "qualifications"! White house will be his mythical Alamo.
Also "making fool of himself". Infront of whom? World leaders? Journalists? Liberals? Those who are no his base anyways? World Media?
Ask yourself, do they even matter to him?
There's his core voter base that will accept any and all of his antics. But the ones putting him in power are different, and do it for different reasons than absed on his ramblings.
His credibility is lost when he attacks institutions, not merely the media or foreigners or believes in pseudo-science and even nonsense, all that is merely politics and everyone "relevant" know that already.
He delivered in terms of economy. That's what matters most. He shouldn't attack what represents America itself, else he will lose the voters that are needed to swing elections in his favour.