It is clearly a scam where he donates $X then quietly steals a multiple of it.
http://money.cnn.com/2017/10/12/news/secret-service-mar-a-la...
I too wish I could set my travel plans then charge the government.
Oh and:
https://www.google.com/amp/thehill.com/homenews/administrati...
That right there covers his salary "donations" for 8 years.