He lost because he said a bunch of really stupid stuff and was convinced that it wouldn’t matter...
I’m a Trump supporter who wishes Trump would leave Wisconsin behind. He lost for some good reasons: 1) No ground game in a state where ground game counts, a lot. 2) Very disciplined state Republican party which is firmly in the “Never Trump” camp. 3) Late start in trying to reach disaffected, less political voters. 4) Complacency.
If lessons are learned and acted on it is plus for Trump, if not it’s a wasted learning opportunity.
You could see it coming from the outset though. Right after he said he could shoot someone dead in Times Square and it would do nothing to his popularity you knew he would up the ante until he hit the ceiling.