Hamas may have support but they were elected 18 years ago and haven't held an election since. 50% of the population of Gaza are under 18. The vast majority of citizens never voted for them or anyone else.
Saying that, they're the only group willing to do something to change the abhorrent conditions they live in under Israeli occupation, so I can see why they would support them. It's quite likely they don't even know the scale of the atrocities committed in their names.
It's been a tragedy waiting to happen for decades, as horrifying as Hamas' attacks are, the body count pales into insignificance given how many Palestinians have been murdered by the IDF.