Justin Raimondo is the go to source when it comes to matters like this. If you don’t check out Antiwar.com and follow Raimondo’s Twitter feed regularly, you should.
Here he suggests that Trump was motivated to pivot on Syria to help call off the dogs at home regarding Russia. I’m personally torn between whether this is a genuine pivot and something Trump actually supports, or if they got to him. I lean toward the latter because it is so contrary to everything he was saying in the campaign and before. Check out his now deleted Tweets on the matter in 2013.
Here and here Raimondo discusses how an element of Trump’s base is in revolt over Syria, and how, conversely, the MSM enthusiastically supports his bombing of Syria. You gotta love that – “liberals” for war.