Who was quite likely a suffering paranoid schizophrenic. who truly believed he was.
I'm not a doctor, but I have studied schizophrenia. Many people who suffer from it never realize they have a problem and never seek help. A very common delusion for them is to believe they are someone famous such as Napolean, The President, God or Jesus. Usually they aren't dangerous, except perhaps to themselves. However, they have difficulty fitting into society, and it rather easy for them to wind up homeless. There are medications that help, but those suffering often never get treatment or discontinue taking their medication. The movie "A Beautiful Mind" covers some aspects of schizophrenia and is worth seeing just to help understand how easy it is for someone suffering from it can go astray.
In that meeting at the restaurant, both individuals were exhibiting various mental problems, and one ended up "converting" the other in the process. A psychiatrist could have had a field day with this.
Sadly, both individuals probably still need help...