That's what I thought as well, but after reading more about it, it sounds like this has been a gradual disappearance. He would show up intermittently at meeting

That's what I thought as well, but after reading more about it, it sounds like this has been a gradual disappearance. He would show up intermittently at meetings and never commit to actually getting anything done. His answers were always "I'll look into that later" and later never came. I still hope that he's just burnt out and sick of the project versus being unwell or worse.