[bigbizisverywyz]

+1 to your comment.

I suspect they are feeling stressed because they're the main goto person on the product, and with enough random bobble heads running around trying to commit sacrilege on your codebase it quickly becomes a problem of control to maintain the quality you've so strongly instilled vs allowing the product to progress.

Their best path to get out of this bind I'd say is to slowly try to make themselves redundant on that product, choose a victim dev to be your successor and gradually disengage. Possibly a new product or project will be started and then they're free to get involved in that instead.

Also learn how to interview new candidates and get involved at that level, getting good (even better than you) coworkers is a great way to influence the whole company culture and make your work life much more pleasant.