Trump has no doubt committed some mind boggling unforced errors, and has allowed himself to be baited by the media/Democrats several times into going off message. Perhaps it will turn out that he was the weakest candidate against Hillary.
But I don’t buy for a second that he’s the only one who was capable of losing to her. National demographic trends (fueled mostly by decades of mass Democrat-importing immigration) favor the Democrats. She, or any Democrat, probably has a floor in the mid-40s nationally, and that floor is rising.
We can’t know for sure how Hillary, the Democrats, and their media allies would have conducted a campaign against a GOP nominee other than Trump. We can’t know how effective it would have been. Maybe with the unlikeable, dishonest, corrupt Hillary at the top of the ticket it wouldn’t have worked well enough for them. Or maybe it would have. They sure did a good job trashing Romney, who now of course is held up by the same Left as a model of what a Republican should be.
Also, it’s not like the other Republicans had a huge lead over Hillary in the head-to-head matchups before Trump won the nomination. Well, Kasich had a large lead as he was so fond of telling us, but part of that was surely due to the fact that none of the Left’s guns had been set on him yet. Rubio was up by 3-4 points if I remember correctly. Jeb was either even or within a point up or down. Cruz had fallen behind like Trump, though not by as large a margin.
Thanks largely to mass immigration, the days of easy GOP wins and landslides are over. It’s only going to get more difficult from here on out, which is why Hillary would likely win reelection in 2020 if she gets elected this year.
Your statement is why Trump's candidacy, and hopefully him winning, is so important. Trump has the capacity to alter the voting behavior of many demographics. This single election could potentially realign the entire political landscape and alter the alter the propensity for specific demographics to vote in a particular way. No other candidate running was capable of doing this.