Actually, the real-world reason for House of M was simple: Marvel had created way too many mutants over the years, and they needed to cut them down to a manageable size. Also... no fallout? The Day after, Generation M, Son of M (and its direct sequel, Silent War), Sentinel Squad O*N*E, the 198, Deadly Genesis, Endangered Species, Messiah Complex... there was plenty of fallout to House of M.
And please, let's try to avoid discussing the personal life of Bendis, that's of no concern to us.