It was land that Trump planned to build a golf course on. He couldn't get zoning/etc. approvals for the development, so he donated it to gain the tax write-off. Given the zoning/approvals issue, the $100 million appraisal is optimistic, at best.
Also, I wouldn't be surprised if Trump wanted his name removed from the thing. The park has been closed for five years, and is not maintained. It's a shambles (I drive by it now and then). Why would he want his name on it?
So, instead of having a nicely maintained Golf Course bringing in Revenue to the City, the Politicos chose to not allow it to be built.
Faced with the Politicos blocking him from Developing his own Property, Trump gave it to those same Politicos (with the Lawful Charity Tax Deduction) who proceeded to let it go to hell.
Boy, those crafty Politicos sure showed Trump what’s what.
Is this a great Country or what?