The Hamas leaders are all very wealthy and and on't live in Gaza. Same as the people running the Taliban - they don't live in Afghanistan. It's believable that they made money from these nasty acts.
The goal is not wiping out Hamas entirely but removing their strategic capabilities within Gaza.
The IS being active in the middle east isn't a huge problem for the US but if they had a base in Cuba you'd for sure have the military there removing it asap...
Hamas really are simply the worst. Don't mind the Iranian propaganda teams on here - those guys will just cry whataboutism and ignore any Hamas war crimes because it's literally their job