What impacted Halo 5's sales the most?

[ethomaz]

small44 said:
Install base,too bad we don't have Halo 1 and 2 first week or month sales

Halo 2 did ~3.3m first month NPD.

BTW Halo 1 just did low numbers because it was launched with Xbox (bundled) and it sold to almost all Xbox sold in the first week... the Xbox launch was not that great.