This.

You beat me to posting this quote.

Riddle Sr. doesn't care to rule magical Britain, and will use this to rid himself of his Voldemort persona. Eventually he can reap the fruit of whatever magical research Harry!Riddle Jr. does, as well as have interesting challenges with him. I'm highly confident he doesn't want to restart the wizarding war (which he couldn't make challenging for himself no matter how hard he tried).

Pure speculation: similar to cannon, Harry will survive Voldemort killing him by coming back from Limbo (possibly the Riddle Horcrux Network).