ISIS leader in Afghanistan - not the ISIS leader Al-Baghdadi

That said, all the talk about how there seems to be new leaders forgets that leaders aren't easy to find.

Sure, someone will end up taking their place - but that doesn't mean they are as effective or capable as their predecessor. Not everyone has the same charisma/people skills or the same level of respect - and as thus, new "leaders" are often less capable than the ones they replaced. Look at the shell of an organization Al Qaeda is today, especially after Bin Laden's death.

And of course, bombing works if is just one part of a bigger strategy - you stop/minimize the power of those who seek to destroy the longer-term social/political/economic reforms necessary to push them to the fringes. As this study from Harvard says:

Leadership decapitation significantly increases states' chances of tamping down militant violence and defeating insurgencies. As such, it should come as no surprise that decapitation is an extremely common policy, regardless of the ethical objections and legal ambiguities that surround it. Despite the evidence of leadership decapitation's effectiveness, scholars and policymakers should consider what it is not. Although decapitation's impact may be significant in many instances, it is not a silver bullet; other factors will matter greatly in most cases and be decisive in many. Decapitation can help states' efforts against militants, but it is more effective as part of a larger strategy than as a stand-alone tactic.