If attacking Rafah is so important to Israel's war effort, why did they wait till now to do it?

If their goal is to eliminate Hamas, it doesn't make strategic sense for them to attack Rafah now. It would have made more sense to attack in the couth first, because that would have cut any potential supplies smuggled from Egypt, and reduced escape possibilities for Hamas leaders, and would have made it more difficult to move hostages around.

That makes me think eliminating Hamas and rescuing Hostages are not the only goals here.

My hunch is that by attacking the north first, they hoped many Palestinians would flee to Egypt, and the hope wasn't to "keep them out of harm's way", it was the hope that they would permanently leave. That seems to be a general strategy of Israel since the beginning to hope that Palestinians would simply go elsewhere if the fighting got too rough or their land was encroached upon.

Logic points towards the unstated goal of Israel is to re-settle Gaza. Those in charge now seem to still hold anger over pulling Israeli settlements back in 2005, and to think those leaders are now "over it" is a foolish assumption. The only thing stopping them is western pressure, from the United States, UK and others that currently support them.