There are generic food factories that supply supermarkets and supermarkets frequently change factories to get a better deal. Years ago I remember baked beans in Lidl having a weird flowery taste which I disliked and then they changed and they were pretty much the same as the basic baked beans from other supermarkets like Tesco, Sainsburys,
Morrisons etc. So they just changed supplier but the label stayed the same I think. Sardines is a good example as whoever supplies those seems to vary enormously, I guess there are multiple factories around the world and Lidl seems to vary from terrible quality sardines to good quality.