That count is not Palestinians killed by Israel, it's Palestinians killed by Israel whose bodies were brought to a Hospital and officially identified (i.e. matched with their state issued ID number).

Israel blew up most of the Hospitals. They also targetted the emergency vehicles that amongst other things brought the victims to the Hospitals and stopped fuel from getting into Gaza so those vehicles still intact couldn't operate and similarly for the diggers that could be use to dig up people under destroyed buildings. Israel also has been blowing entire appartment buildings (often using the 2000lb bombs provided by America and known for their massive collateral damage) en masse, so many many corpses were never dug out from the rubble, especially by the point of the war when there were far more than just a few appartment buildings blown up (and all that takes is to check Google maps nowadays to so just how massive the percentage of blown up appartment buildings is by now).

So the real number is likely many times larger than those 75k, possibly by a factor of 10.

In fact an estimate of the deaths published in the Lancet Medical journal at around 1 year after the start of the war placed the number back then at around 200,000 (edit: as per the info provided by Garfunkel@lemmy.ca below it's 186,000 - see here).