I mean, it’s obviously an outrage-bait cliffhanger that’ll be resolved by saying “Mjolnir knows the real Cap is worthy” or something, but Marvel is really treading the line here with this event. It’s been established that Thor could no longer lift the hammer because
he believed Nick Fury’s words that Gorr the God Butcher was right,
essentially Gods were worthless.
Maybe, Cap is so firm in
his beliefs and believes he is right that the hammer recognizes that. The
hammer didn’t want Thor to lift it because he didn’t believe in himself.
At this point I just assume Mjolnir is just fucking with us all and took
a liking for trolling people ever since Original Sin. It’s the only way
to make all the bullcrap surrounding it work.