Are there any kinds of nerds that are more intense than video game nerds? Oh, right: theatre nerds. So what happens when you put the two of them together? You get a dude dressed Altaïr belting out some dulcet tones about how he needs to take a "leap of faith," obviously.
Assassin's Creed: The Musical comes from YouTubers Inside Gaming and Machinima Prime, the (slightly) more dressed up part of the popular gaming-themed video entity. It's more just silly fun than any sort of serious deep cut for Assassin's Creed fans. But at least they can recognise that nobody — nobody — likes playing as Desmond.
Also the Ezio song is perfectly silly. Why does he sound like he's trying to start a square dance?!?! He's from Italy!