It's not really related to being personal and I think that makes it way too complex. Trump has a reflexive anti-war streak because he's afraid of making a mistake on it and looking bad. He got Iraq "right" simply because he was posturing against W. and conventional wisdom from a position of no consequences and turning out right helped reinforce this. He'd otherwise never taken stances on anything like that. He was always a frontrunner.
That article about everyone in the departments being upset with Trump for not warring enough actually said this without saying this. All the sources essentially said that when they get to the point where they have to ask Trump "yes or no" he disappoints them by siding with "no, not yet" and they have to go be diplomatic. There was always lots of talk that Obama reflexively said "yes" because he was afraid of appearing too anti-war or whatever. Especially when Clinton was Secretary of State, and when Kerry came in it changed as Kerry is less hawkish than Hillary simply because he's a ditherer while she decides and then sticks to it and will literally murder people who dare her to change. Anything that lets Trump "not decide" or punt is basically what he wants.
In cases where they can essentially do as they wish without asking due to longstanding situations, the departments do, and Trump eagerly takes credit for the successes even though he didn't order anything or make any decisions on it.
Trump doesn't see trade or any other kind of foreign policy as the same, he was quite steeped in the military ethos coming up and while he is totally disregarding of everything about it on a personal level, he was always said to be super respectful of the concept and I think that leads to him on some level recognizing the potential and literal human cost (especially coming of age through Vietnam) that contributes to his hesitancy. He doesn't want to look bad causing deaths of soldiers more than anything. I think he also likes to think that the troops love him and he's reluctant to introduce anything that may contradict that like killing a bunch of them.
Wars through Twitter are the perfect Trump War. Actual wars, not so much. That's the frustration that someone like Bolton has, that then gets into the press about how Trump is fucking up good opportunities to bring lesser nations to heel.
