Trump is probably on the list, so he has to protect that. The Democrats had it during their entire presidency; even if they didn’t want turmoil during their time in office, they could have released it after their presidential defeat and before Trump took office.
Because most of their big money donors are also on the list.
If someone hands you $50,000 a year with no questions every year, it’s hard to say no when they squeeze your hand and ask you to reconsider releasing it.
Especially if even if you released it it probably wouldn’t change literally a single thing.