This contrast between a person and the music is often true. Wagner was a truly awful person, an antisemite, racist and overall shit. He put it about that Brahms' music was based on the screams of birds that he shot with "A Tyrolean bow". An outright lie just to discredit a rival composer.
Somewhat interestingly he was a cross-dresser; even the usually staid and formal Wagner Society accepts this.
He was also Hiter's favourite composer. 'Nuff said.
If you could bring him back from the mid 1800's and interview him today, I'm sure he would be found to be an abominable person in many ways.
In spite of all that, Wagners music, particularly the operas, is utterly marvellous. In addition to the epic 15 hour Ring Cycle (took him 25 years to complete it), there is Die Meistersingers, Tristan und Isolde, Tanhauser, Lohengrin just for starters. Seen them all. Awesome.