I'm not an expert on that story, but from what I had read at the time, the issue was that some of the money went to other charities and not all of it went to the hospital as was claimed in financial records.
Apparently if you raise money for one charity and then give some of the money to another charity, that's fraud.
An excerpt from a recent story I just Googled about it:
The charity did in fact raise a serious amount of money at the golf event that year, some $1.8 million, according to
federal tax filings, while maintaining an impressive expense ratio of just 14%. But not all of the money went to St. Jude Children’s Research Hospital, a renowned pediatric cancer center in Memphis, where the Eric Trump Foundation had been telling its donors their money went for years. In fact, St. Jude received $1.2 million, $240,000 covered expenses and more than $200,000 went to other organizations, most of which had no programs to help kids with cancer but did have strong ties to Trump family members and interests.
Ten thousand dollars paid for tables at an event for another nonprofit, the Little Baby Face Foundation, which honored Eric at its annual gala one year. Some $37,000 went to the Staten Island Zoo, which
at one point said the Eric Trump Foundation had helped to donate three arctic foxes. Another $15,000 went to a charity that supports at-risk Jewish children in a southern Ukrainian city.
And that was just in 2014. From 2011 to 2015, the Eric Trump Foundation donated more than $6 million to St. Jude Children's Research Hospital, but it also doled out over $500,000 to about 40 other charities, while assuring donors on its website that all gifts supported St. Jude.
https://www.forbes.com/sites/danale...ds-with-cancer-then-gave-to-different-causes/