I don't have any details, but maybe this post from a few weeks later about his mental state is relevant? https://balazsorban.com/blog/depression-and-oss

I can't imagine the pressure of running a popular OSS project, even if you have support from a company to make it your full time job.

Oh yeah I totally get why he'd step away, especially after the ambitious goals the project set itself. That said, I haven't seen mass panic yet, so I'm wondering if people are confident someone else has picked up or will pick up the slack, or if it's just flying under the radar.