Claiming Western governments began bombing ISIS "because they decided they needed the target practice" would certainly be an exaggeration.
The reality is sinister enough, there is no need for exaggeration, and the reality, as I understand it (or I think I understand it) is that Western nations are bombing ISIS in order to provide military support to essentially the United States of America (their NATO ally) who illegally invaded Afghanistan in 2001, and Iraq in 2003. I believe lawyers call this "aiding and abetting a crime".
And it seems to me the fundamental reason why the U.S. (with some allies) invaded Afghanistan and Iraq (after 9/11) was to help Israel "steal" more land every month to the Palestinians. This has been basic U.S. policy for about 50 years now, and is (and has been) probably the basic cause of much of Middle East terrorism (at least, before the year in Yemen, which is more related to opposition and rivalry between Saudi Arabia and Iran).
Nevertheless, in my opinion, the ISIS people and the Taliban (and even the Iranians) should also make an effort to evolve and change: they should adopt democracy, human rights, freedom of religion, education for girls, right to divorce, right to dress as they like for women, without a dress code imposed by elderly male clerics, and so on. As long as the Taliban and ISIS do not adopt basic human rights, there may unfortunately be some legitimacy to Western occupation (or military assistance).