It's one of the great mysteries of Mega Man fans. Why is there no trace of Mega Man, Proto Man, Bass and the rest in the X universe?
All we really have to go on is this translation from the 'sort of canon(?)' story from the Mega Man Zero collection.
http://www.themmnetwork.com/2010/04/09/does-the-rockman-zero-collection-storyline-explain-everything/"At least 200 years ago
The birth of X
When an incident occured where an unknown computer virus came from space and causes robots to become violent and riotous, Dr. Light completed the battle robot “X” worrying about the future of Earth. Hypothesizing X could battle robots infected by viruses, he gave X the perfect virus counter-measure. Meanwhile Dr. Light developed a great number of armors, but this presented the possibility of X becoming a threat to mankind. To confirm the safety of X’s cognition program, Dr. Light sealed away X in an analysis capsule.
1XX years ago
The birth of Zero
Zero was produced by Dr. Wily, who schemed at taking over the world. But he contained a flaw in his cognitive program that made him violent and unwilling to obey instructions, so Dr. Wily himself sealed Zero in a capsule.
1XX years ago
X is discovered
X is discovered by Dr. Cain, having been buried underground for 100 years."
So did all of the Mechanaloids get infected and kill each other, as well as try to slaughter the human race? Was Mega Man turned into a violent, crazy killing machine?
They -also- talked, in the Art Books, about how it was Dr. Light's fault. He created X with a 'suffering circuit' that was reproduced incorrectly by Dr. Cain, which means that the Maverick Virus didn't exist before reploids.
So were there two totally different viruses? And what about the Zero virus where people say it was created by Dr. Wily?
Proto Man had a nuclear power cell, so unless he was fully repaired by Dr. Light or another scientist of equal or greater skill he'd have run out of power. Auto had a cameo appearance in X3 which only confuses me MORE.
It's now canon that Zero was never released by Wily before he died, so it's unlikely that Zero killed the main cast.
There was an end to the 'robot rebellions' at some point in 20XX, which I originally thought had related to the original Maverick Virus, but with the whole 'it came from outer space' thing, I can't be sure. All I know is Zero was created AFTER X, and AFTER the origin of the first Maverick-esque virus.
Does anyone have any other information to add? Or some clarifications and/or theories?