The why would be in deed interesting. But without any information it's quite useless to speculate.

The sad part for me is, that he was contibuting to this forum, giving answers and statements. And I don't think he is allowed to give more information after leaving Jolla.

And even if he is allowed to, I don't think he will do. Talking about internals of the company you left, isn't a good application for your next job.