Laotuo, could you help again?

Laotu, thank you very much for the response yesterday. If my husband will take the better offer, he will need a good reason to refuse the old offer. what is the best reason for this kind of sudden change? family reason (wife does not like moving)? no need to move? any other reason?
How can he let his old boss understand it? His old boss will be a very good reference for his future.

Postdoc is not a good job. Hopefully, we can find a good real job soon.

Best wish,