1. He had an election to win when he first blocked accession.
2. The US likely had a little chat about the Hamas leaders staying in Turkey. They were asked to leave after the attack. Continuing to block Swedish accession, when you've been harbouring Hamas, is a bit too embarassing.
3. The media's distracted by the Israel/Palestine thing, so it's a good time to bury an embarassing u-turn.

Seems like he just wanted to seem tough for the election back in May. The whole defender of Islam thing probably garnered him a few extra votes among conservative and moderate voters.

I don't think he wanted to stop it, he just wanted to stamp his feet. It's not getting as much attention now with Israel in the news.

Sweden recently said they'd give fighter jets to Ukraine if they were accepted. That probably added pressure