Potential Spoiler? (Theory)

Vecna could have easily killed Joyce but why didn’t he? It seemed like he was almost gentle with her as he moved her out of the way. The reason could very well be what Max described when explaining to Holly what she saw in Vecna’s memories.

A young Joyce handing out flyers to students (Including Steve Harrington’s parents) at her school to get people to come to her play and as you saw the name Henry Creel was on the flyer which means Henry knew Joyce.

Maybe Henry has a soft spot for Joyce because she was the only one that was nice to him. This leads to my next theory which is Vecna purposely giving Will his 001 powers in hopes that Will will join him in reshaping the world like he had hoped Eleven would do.