Because a jury found him liable. Doesn't mean he actually did it.
And I doubt you would consider this a fair outcome. This allegedly happened over 30 years ago. She couldn't even identify the year that it happened. Take Trump's name out of it. Do you think it's fair for a man to have to defend against 30-plus-year-old allegations where the accuser cannot identify the day, much less the year, that it happened?
Only $5 million of the liability settlement is based the sexual abuse by Trump of E. Jean Carrol which happened decades ago.
The $83.3 liability settlement was for defamation of character which happened beginning October 2022 when Trump published a "lengthy post" on Truth Social against E. Jean Carroll, which included a June 2019 photograph of her. Carroll would later successfully claim this post as defamatory. Trump's first defamation liability ruling by a jury was in 2023.
Trump continued to make public statements denying the sexual assault and also made comments which were later found to be defamatory. In 2024 a jury once again found Trump liable for defamation.
Each was a separate case. Both times, different juries found him liable.