Current day weapons manufacturers are able to bump up their profit margins to insane levels because it's about the easiest thing in a society full of idiots to get spending approval on. Especially when there is an enemy people are afraid of. In the case of Sunni rebel extremist factions, most notably ISIS, they're getting pounded by the Syrian and Shiite forces.
Iran is a next good target to justify increased military spending. The Democrats had been making efforts in aiding in the liberalization of Iran by lowering sanctions and building treaties. This is counter-productive to the weapons industry which dropped from the ~745 billion to about 565 billion valued in 2013 USD under Obama. Having Iran, and the 90 million people living there, as a threatening enemy would mean greater justification to spend much more on the military.
Attacking easy targets in Yemen and Syria that would piss off Shiite cultured people is one method of making Iran and Iranians hate the US more, and increase the potential trigger for an attack.
Causing other countries to attack and break treaties is about the oldest trick in the book, next to prostitution.
It's not difficult to see what his goal is. This method has been around since the Delian league in ancient Athens where they would attack various city states in hopes that they could trigger other powers (the Peloponnesian league, in the major case) into breaking treaties. The US employed a similar strategy when the ambassador (April Glaspie) pretty much greenlit Saddam to attack Kuwait, conveniently in the closing period of the cold war.
I don't think North Korea is going to be a target unless pissing off China is seen as a good way to jack up military spending to even more astronomical levels, or spending on some other kind of industries the Republican donors have their hands on. It wouldn't be as good of a target as Syria or Yemen.
I don't want to attribute anything to Trump, because let's be real here, he's not the brains behind the party; aside from his frequent appearances of stupidity (he makes the Bush brothers look intelligent by comparison), he also lacks anything beyond the most basic functional literacy. Unlike Obama, Trump is a figurehead: his job is basically golf, signing documents he is incapable of reading or comprehending, and yelling stupid things on TV to impress bumpkins and other asswits.