I think hes just getting increasingly frustrated and flabbergasted, because he spent his entire life in a bubble surrounded by yes men telling him he could do whatever he wanted, and get away with whatever he wanted, and had a constant stream of sycophants up his ass praising him and everything he did.
but since hes got elected president, he… for the first time in his entire life, has met with constant criticism, with constant roadblocks, with constant "NO"s for almost everything he did, does, or tries to do… and its wearing on him. Hes at the end of his rope, he doesnt know what to do or say to elicit the praise he wants from anyone other than the ugly peasant folk that adore him, and that he absolutely detests, and thats leading him more and more to frustrated irrationality and revealing ever more of his true self and opinions.