How can we teach our CTO to understand his new role?

Hey everyone, I've been working with a guy who has been a solo developer for most of his life and owned his own company. After a merger, he is now the CTO of a company with an existing developer team.

The struggle we are facing now:

- He is not responsive at all, neither via chat, nor email, nor any other communication tool. So we often have to write him via chat "Please look at this PR, I left some comments" etc...

- He doesn't know how to delegate and often says "I'll do it" but then it takes weeks to finish

- He has thousands of unread emails in his inbox

- When he writes tickets, the details are often unclear and hard to follow for other developers

- He codes way too much for a CTO, in my opinion, and his code is a bit messy compared to the other developers

Since he is a really nice person, we all want to give him feedback that makes him understand his role better, and to become more efficient and avoid being a bottleneck.

Has anyone struggled with this in the past, and found a solution, or at least a way to see small, but steady improvements? I know that changing another person is one of the hardest things one can attempt to do, but at the same time I know that he is motivated to become a good CTO, but currently just doesn't know how yet.