In fact, it is far from clear and obvious as such. Indeed, what is clear and obvious is that choylam is very much correct. This is despite what some internet pundits might want you to believe.
In addition to whatever other points where previously made, the mere fact that so very many Gedolei Yisroel pronounce it as choylem — for davening, no less — is in itself one of the best proofs of this.