I blame the media, as they have enabled (and even encouraged) Trump to get as far as he has.
You see, the media (specifically the for-profit media) care about one thing above all else. Ratings. This is more important than the future of our country, more important than national security, more important than anything else. Because their end goal is to make money, and ratings translate into profit.
Trump has been a gold mine to them, and they’d like to keep that running for as much mileage as they can get.
It’s also to their benefit to make this as close a race as possible, as that keeps people tuned in. So even though by all logic a candidate with experience, an impressive resume, workable plans, and realistic promises should have no problem handily beating a candidate with none of those things plus a demonstrative display of cluelessness, the media will allow Trump to go unchallenged on even his most outrageous utterings, whereas every single skeleton (even all the imaginary ones) of Clinton’s gets breathlessly reported ad nauseum.