Good point! He only told some 30,000 lies during his first term. https://www.washingtonpost.com/politics/2021/01/24/trumps-false-or-misleading-claims-total-30573-over-four-years/ Whatever he says you can take it to the bank! Or maybe to the ATM, okay, okay maybe the toy cash register.
It's projection. The guy said the dumbest things during the pandemic, and he shouted "they're eating the dogs, they're eating the cats" during a debate. Rumor has it that one of his Wharton professors thought he was dumb and that his family paid someone to take the SAT for him. Not to mention that his father spent millions to bail out his casinos.
When Trump makes up stupid lies like Kamala Harris was born mentally impaired there are a lot of people that believe stupid lies like that. Even many intelligent people believe silly lies like that. I can even think of a contributor on this forum that believes that lie. Why How could anyone believe such an obvious ridiculous lie? Simply because they want to believe it is the obvious explanation.
That contributor is also projecting, and he thinks every woman is dumb. Smart people do not believe Trump's lies. Much of Trump's base is dumb and uneducated; that's why he lost the college-educated White vote, which normally goes Republican. He's few intelligent supporters don't believe him; they just want him to cut their taxes.