Ederson actually replaced Muric for the League cup final win against Chelsea
Muric wasn't our second choice keeper. He was a kid who came back because Bravo got a terrible injury, and whose career has since then been an unmitigated disaster. Starting him vs Chelsea would've been asking for trouble.
Steffen has done nothing to suggest he's not perfectly capable of playing this game, and in the delirium of last night's win it's forgivable that everyone seems to have forgotten that Ederson is extremely fortunate not to have cost us the tie.