What inspired leonardo da vinci to paint the last supper?

There are many theories about this painting and I'm not talking about "The Da Vinci code" by Dan Brown but let start with a fact.

It was an comission by the duke of Milan Ludovico Sforza in 1482 but it was until 1495 that he started painting it and it took him years to finish.

He wanted to give the painting a realistic sense so he had real models but struggled to find a good Judas.

Da Vinci started visiting jails looking for someone with a "criminal" aspect and it is said that when he finally found him he was really amazed by his looks that he used him and then this inspired him to finish the painting.

As I said in the beginning; There are many theories not only around what inspired him but also about the meanings inside the painting. "Leo" was a great artist but also a professional procrastinator which explains the reason why it took him so many years to start it and then to finish it.