Here's a possible answer. It might be a timing issue.
>>>Ciara Torres-Spelliscy, a professor at Stetson University College of Law in Florida, said the risk of paying defense attorneys with contributions is that the FEC or the Justice Department may later decide that it was an illegal personal use of campaign funds. She doubted such a case would be brought against Trump now because doing so might slow the ongoing federal prosecutions overseen by Justice Department Special Counsel Jack Smith.
“But after the Mar-a-Lago and January 6th cases are done, I would not be surprised to see a personal use case against Trump for using these millions in donations that are meant to go to his political campaign going instead for the personal use of keeping him out of prison,” Torres-Spelliscy said.<<<
. . .
Trump's legal problems might get significantly worse before too long.
According to this article, Trump is running out of other people's money (OPM) he can use to pay his legal fees.
>>>Since leaving office in 2021, former President Donald J. Trump has spent more than $100 million on lawyers and other costs related to fending off various investigations, indictments and his coming criminal trials, according to a New York Times review of federal records. . . .
Instead, the former president has relied almost entirely on donations made in an attempt to fight the results of the 2020 election. . . .
The Trump team has said the Republican National Committee won’t pay his legal bills. But
his new shared fund-raising agreement with the party directs a portion of donations to his Save America PAC before the party itself.
Still, the account paying Mr. Trump’s legal bills will most likely be out of money by summer at the current spending pace.
Then, Mr. Trump will have to decide: Whose money will he use to pay his lawyers?<<<
Trump supporters poured money into his effort to challenge his 2020 election loss. That fund has paid lawyers to defend him in his legal battles.
www.nytimes.com
This article provides a good explanation of how Trump has used OPM to pay his legal bills.
His maximum possible delay strategy appears to be moderately successful (if success is defined as "delay trials until after the election") but it is also costly.