Most of the deaths come after the Hurricane passes

Why is this?
Partly because of downed power lines people cannot see that are still hot. A power line can be in the water and not be sparking because it is grounding into the water. But, the nearer you come to it if wading in the water you will get more and more of a shock until you are knocked out and drown.

Also, road hazards like fallen trees or branches you don't expect, boardwalks with pieces of planks missing that you don't expect, roadbeds without sections of it from flooding or surges or bridges without sections of them still there. Or flooded roadways deeper than you notice until you are into them.

So, these are only some of the ways people drown by having to deal with unexpected things. Though there are people like linemen, and firemen and women and police and other personnel who would know how to assess these problems right off, most people (40% to 80%) of people might not be able to assess the danger they are in until it's too late and they are gone.

Also, in flooded areas you also have to be aware of poisonous snakes in the water or alligators in places like Florida, Alabama, or Louisiana or other places also. Because alligators I believe can be in salt water temporarily on their way to fresh water places too. So, not being able to assess which set of problems you are encountering when you might not have seen them before is how a lot of people die needlessly after storms like hurricanes pass through an area.