I think jamming up China's oil supply is part of it. Part of the deep state Grand Strategy.
Though in my opinion Trump personally, his outlook is short term. Fast wins, fast profits. I don't think he cares much about anyone else or else he would act a lot different. He's not altruistic. Make his family a ton of money through grift and then pardon everyone.
I think Venezuela was done first before Iran to get an alternate supply. I don't know how the oil supply is going with that, I know it's the heavy crude, hard to get out of the ground. I know some US oil companies weren't interested in investing in that. It can't be going great or there would be no problems.
Iran is not going well at all. I think Trump thought it was going to be a quick deal, he let himself be convinced by Bibi even while his own generals warned him. Now he can't really win and he absolutely can't lose. Trump isn't really in control anyway, it's the deep state, it's Israel. Trump probably would walk away if it was up to him.