Of course a video would have helped. However, she's Adele, she has proved she can smash with or without a video. The song peaked #11 on pop radio, didn't it? Well video had nothing to do with it.
I mean it peaked at #9 with a BRITs performance. I doubt that would have helped less than a video (which would have been similar to SLY, aka boring).
I was the first one rooting for it and believing it would have smashed. Sales were indeed disappointing due to huge album sales, but what about its streaming chartrun? Album sales had nothing to do with it.