Too many people think that "Amadeus" was 100% factual! While it was a very good movie, it distorted the truth severely.
As has likely been mentioned before. The movie is not based on reality. Its based on a Pushkin play from 1830 called "Mozart and Salieri". Its a short play, just a couple of short scenes. There's subtitled videos on youtube which are about a half-hour... you can probably read a translation of the whole thing in just 10-15 minutes:
Rimsky-Korsakov staged a 1-act opera with the play as the libretto in 1897.
Hollywood fleshed out the screenplay with Mozart's biography to fill time and showcase the composers music but the whole Salieri/Mozart interaction is based on Pushkin and entirely fictitious.