Why are the big as companies seeking total control over the food supply and production?
Because they alone can ensure everyone is adequately fed with the ‘right’ foods.
The big seed tech companies don't control anything except their own patents. They develop new varieties using a variety of methods, including but not limited to gene splicing. They then commercialize and sell what farmers want to buy. Farmers, in turn, want to plant what their customers wish to buy. Most corn and soybeans are destined for animal feed, and feed manufacturers and animal feeders want high quality inputs at the lowest possible cost. GMO's boost productivity and lower costs. This is what drives GMO's.
At what point in this straightforward process does the evil conspiracy come in?
I have nothing against organic producers as long as they don't make false claims. Unfortunately, there is a radical fringe that poisons the discussion. Organics are generally significantly more expensive than their conventional counterparts. This is why "organic" still only commands 1-2% of the U.S. market, despite endless hype. This frustrates the activists, who respond by trying to demonize conventional agriculture. This is a form of consumer fraud; it is intended to gull people into paying much higher prices for a product that is no better, and is in some respects inferior, based on dishonest scare stories about the competition. I hope some future administration unleashes the FTC consumer fraud unit against the professional liars.
As for myself, I vote with my wallet, as should you. When I see "organic" on the label, I immediately check the unit price, and then compare. I prefer not to be fleeced by hucksters. YMMV.