I don't think he ever intended to or cared about it. It was just one of many lies he told to get people to vote for him.
The thing with Trump is, pretty much his whole life has been privileged. Daddy bought his education, gave him a "job", had people around him so he couldn't mess up too much. He's never really faced any consequences or anything, so to him he's been able to do and say whatever he wants with nothing happening to him. Like bragging about committing sexual assault, making fun of a handicapped person, etc. He assumed saying that would be like any other thing he's said, where he never gets held accountable. Or he could spin it into something else, like how he was an FBI informant all along, and pretend like he never really said it.
This is different, and partially it's his own doing. He campaigned heavily on and gave tacit approval to wackos who believe that QAnon is real, that he was going after supposed pedophiles and satanists who prey on children, and now that he's obstructing documents that could reveal some truth to who might have been involved in child trafficking and sex abuse, he won't do it. So some of those angry cranks are turning against him.