1) Legally we would not be justified in killing the innocents on the bus to stop it reaching its destination, given that many other means exist - erecting barriers around the target, using area denial tools like caltrops, or even inserting a special forces team to commandeer the bus. We certainly wouldn’t fire a cruise missile at the bus.
2) This is exactly why we don’t let people with conflicts of interest make such decisions.
3) Hamas never had the support of a majority of Palestinians. It “won” an election in 2006 with something like 30-40 percent of the vote because there were many parties and both Fatah and Likud helped them (albeit for different reasons). Since then support for Hamas has only fallen.
But that was 17 years ago. Half the population of Gaza is under 18. So saying that they “chose” Hamas and that they cheer Hamas on is both false and just an excuse to mete out collective punishment. Justifying such war crimes requires that you dehumanize the victim, which is exactly the whole point.