Why is "Rasputin" treated like a real name now?

Unless I'm mistaken, wasn't Rasputin a name given to Father Grigori by his enemies because it means "desolate"? His actual name was Grigori Yefimovich Novy. It seems that most people think it was his last name. I was even surprised to be playing a game and a surname I could give my Russian character was "Rasputin".

The answer: simply because Rasputin was his family name.

About Novy, this I posted many years ago:

About "Novy":
In Nicholas' personal archives is Rasputin's request, dated Dec. 15th 1906, to the Tsar, to grant him and his descendants to be called "Rasputin Novy". As reason he wrote: "Living in the vilage of Pokrovskoe, my family name is Rasputin, the same family name I share with many other villagers, therefore may rise all kinds of minsunderstandings."
In municipal documents of Pokrovskoe from 1908 is a remark next to Rasputin's name: Grigorij has been allowed with permission from the Tsar to be called by the family name "Rasputin-Novy". Order from the Tobolsk State Chamber from March 7th 1907, under No. 9136 in case No. 11/1907.

Thanks for that info! But then where does the info come from that he was given the nickname by his enemies?