Respectfully, maybe spend 5 minutes reading about it from the horse’s mouth. The Mamdani admin has done a pretty good job, imo, of laying out the case, and explaining the plan for these 5 grocery stores.
* Jurisdictional: Food stamps can't be adjusted by NYC itself (as far as I know), so if they're insufficient this works around that issue
* Store access: Food stamps don't necessarily solve the problem of "there's no grocery store close to me", and if the market can't be nudged in that direction, a direct intervention solves it faster.