Originally Posted by
Glio
At the initial moment of the resurrection, Santo says "professor", clearly identifies Xavier. He is corrupted moments later.
The thing is, Otherworld corrupts all the existing backups in all the existing Cerebro out there when a failed resurrection is done and completely overwrites any traces of the original backups. This is because Otherworld is the nexus of the entire multiverse and when someone dies there, it causes problems.
So, in short: Dying in Otherworld affects resurrection because it is a magical place.