The login wall probably marginally increased whatever signup metrics they were tracking and some middle manager at Quora probably patted themselves on the head for a job well done for that genius idea, but it killed my interest in Quora too. I can't be bothered to try and login every single time and I just started purposefully avoiding Quora links going forward once that was implemented. And it's a shame because the content is pretty great and a site geared around answering questions could be the most amazing source of human knowledge out there. But it doesn't work if you purposely try and restrict the content.
It briefly had hn like quality to it.
Then they got acquired (I think) stuck a login wall in front of it and the spark died.