Why is it a PR fail to show Sinwar? For a start, the main reason to show the pictures would be so that people actually believe he was killed. He was such a secret fugitive that rumours he had died circulated before, simply because he wasn't in touch with anyone. It would have been very easy to deny he was missing for a significant time.
I know that Arabic twitter is attempting to laud him as a hero, but I would actually think that it's pretty embarrassing for Hamas that the mighty Sinwar died alone, and especially in possession of fake ID (taken from an UNRWA teacher who has been in Egypt for months), 40,000 shekels, and a packet of Mentos. I would be absolutely furious if my kids were starving and here was the person who had failed to protect me, with fake ID, sweets, a protective vest and unlimited cash. It's ironic that his death was so insignificant that the soldiers didn't even check his identity until the following day. He didn't even fall to some top commando unit - according to Israeli news reports the relevant shot was fired by a new recruit who hadn't even begun their military service on 7/10/23.
But above all it's a colossal strategic asset and PR win for Netanyahu. He has the 'victory' photo that will possibly serve as an off-ramp from the war if the international community plays its cards right. It's hard to imagine any other goal for the IDF in Gaza other than returning the hostages. Sinwar's body may serve as a bargaining chip for the bodies of soldiers held by Hamas. Hezbollah is on a back foot after losing its leadership. Iran is waiting for Israel's response. This is a very significant opportunity to negotiate an end to the war.