And he's doing his marketing with the main marketing channels against him.... The MSM, Tech/Social Media, etcTrump is an excellent marketer and after decades of doing you can see it play out. While it all seem very elementary on the surface, and it is, that is the secret to it all. Don't over complicate it, because it works on a heavy majority of the people. For the few that it doesn't work on then you can get down to the details more. It works very well in human communication to get what you want from people.
If someone supports you, even if you have had past disagreements or even if you have current disagreements, you throw ego aside and praise that person. You one up their positive sentiment and you will persuade them to your side.
If someone doesn't support you, you simply discard them and their opinion as not important. The opposite of love is not hate, it is indifference. You keep everything positive and with news of disapproval you discard it and say "meh, well, their opinion is not important anyway".
It works very well in all interactions. I don't see him as dark triad. I just see him as an excellent marketer/communicator and someone you can learn from with his interactions with others.