I think it's more complicated than that. Also from the article:

> He is working with FareShare, a charity that distributes surplus food to those in poverty, to get the extra brassicas and potatoes to those who need them.

So at least some farms have had the resources to get this surplus out to people.

> Consumer demand is also to blame; the mild weather means people are not yet in the mood for sprouts and cabbages.

Perhaps demand wouldn't be that high even at a low price.

> Whilst supermarkets are adapting by offering vegetables – such as potatoes and brassicas – of a smaller size, many are refusing to pay farmers a price that would cover the cost of production.

Perhaps the price wouldn't even be that low if you bought direct from farm. Operating costs for farmers have also been affected by inflation.