What's remarkable is that a businessman in Trump's position was so bad at communicating, even taking debate inexperience into account. How can you position yourself as a tough negotiator if you can barely form a coherent sentence under the spotlight? You could see the germs of potentially potent attacks on Clinton's credibility re: foreign interventions, black lives, the economy etc, yet each got little more than a cursory mention before jabbering onto a different tangent.
Even his 'I pay no taxes, it's good business' stuff could almost have worked if he'd linked it to people like Clinton and husband being in the corporate pocket (and Trump's wedding) leaving loopholes open for big business to exploit. Instead, he just sort of boasted about paying no tax, which might play OK to the arch-Republican crowd, but likely won't be a hit with the undecideds.
Any semi-competent debater could've torn Clinton to shreds on virtually every issue, but she was given a clear run to the finish - and while she had some decent plays provoking his ego, she still struggled to come across as anything more than as over-rehearsed and insincere, especially that painful Trumped Up Trickle Down bit. As many have said, these are two candidates who could not have been luckier to face each other.