Wheat has never really been used as a store of wealth in modern times by mainstream financial participants. They would rather just stick with the highly liquid gold market and in times of inflation, oil.
Note the price of wheat actually fell the last time the market "...slowly collapsed" back in 2009.
Wheat is a supply and demand market. Yes. The advent of funds has meant temporary distortions in the short term and heightened volatility, but fundamentals (stocks to use ratio etc) always determine value in the long run.