Re: What happens when all nodes on the blockchain go offline?
There is more than that the longest chain wins, it's actually the longest valid chain wins.
Completely agree that it's the longest valid chain that wins. But it is not always possible to know if a selfish transaction is invalid. The validity rules embedded in the software can check for some invalid situations but not for every possible invalid situation. If validity rules were able to check for every invalid situation there would be no 51% attack (https://www.investopedia.com/terms/1/51-attack.asp).
... they may have to accept those blocks with selfish transactions ...
Note the use of may purely for that reason
