User blog comment:Fedguy/How the villains could have won (Crisis)/@comment-27700324-20171203050517

I'll tell you a couple of reasons why this wouldn't work.

A.

Supergirl takes a while to be drained of her powers for them to save Overgirl. So in that time Alex, J'onn, The Legion os Superheroes, Guardian, and Superman would be able to formulate a plan of attack.

B.

When they are attacking the wedding, everyone knows Kara has been taken and therefore the Nazis are no longer a suprise.