I don't agree with you. There were other candidates who were entirely capable, but Trump sucked all the oxygen out of the room with his belligerence and bluster, and the circus-goers and the media ate it up. Media helped enormously by giving Trump all the attention that malignant narcissists craves. I read something about the early debates being a case of "parallel taunting," and that Trump was able to use that (heck, he drove it) to his advantage.
Agreed ... I believe that ANY of the other candidates were capable of performing the job ... even if I didn't necessarily agree with them on every policy.