Just because an action one takes benefits another does not mean the action was taken to benefit the other. Completely different agendas at play between Trump and Saudi over dealing with Assad. Likewise the dems are praising Trump for different reasons than those that motivated Trump to action.
Whatever Trumps motivations, the results are pleasing to McCain, Hillary and Saudis, who want Assad to fall. Also pleasing to the mainstream media, which hates Christianity. Assad protects Christians in Syria from Shiite jihadis, so he is hated by western liberals. That’s why, whatever Trumps motives, he’s getting praised by all these libs, media, and Saudid