The headline seems to be mixing two trends in food randomly. The drop in meat & milk is likely independent of vegan trends - the $ figures are different orders of magnitude. This isn't substitution at all, so there is no reason to think they are interacting.

Europe is probably being hit by some sort of hardship right now meaning people can't eat as well as usual. The UK seems to be being hit by an energy crisis for example, although they also seem to be having a much worse time of it than mainland Europe. Per capita figures are lower than China and it might drop below the global average in a decade if the current trend keeps up.