That is, for religious reasons jihadis are fighting only against Muslims? Honestly, I thought that a professional terrorist / Muslim fundamentalist will kill Christians with the same joy as well as his co-religionists.
Christians are people of book, muslims dont hate them like you seem to think. Jihadis will only go to Ukraine if it was muslims country and Russia christian invaded it.
In syria jihadis have other reasons as well, they think they are liberating muslims from Shia Asad.