I'm sure there are a lot of different reasons.
Some probably like his tough talk in regards to ISIS.
Some probably like his willingness to deescalate tensions with Russia.
And some probably just want to stick it to the establishment.
What I cannot figure out is why any self-respecting veteran would support Clinton.
After all, she's been Al Qaeda's best friend for many years. Without her, they never could have set up shop in Iraq, Libya, or Syria.