Let me try my understanding.
You opened a FB account long ago. The only flying activity has been a cheap AF flight earning 140 miles in October 2019.
Those miles expired by the end of October 2021.
Given the lack of flying activity and zero remaining miles, FB decided to close your account, probably at the start of November.

Just before closure you transferred from AMEX the exact number of miles needed for 2 business class tickets. These were issued normally.
There is no reason for such a credit card to prevent closure of the (flying) inactive account. To the contrary, AFKL do not like to see an account used solely for getting awards from cc transfers. You probably had zero flying or cc miles by the end of October.

Nothing unusual here. Your tickets are issued prior to closure and valid.