I'm not an expert in this, but I think that the evil VC game plan is to try to make their portal the default first stop when ordering food. If they can get to that point, then they can start transferring the profit from the restaurateurs to themselves. This is more likely if people are indifferent to the specific place they order from after they've selected a dish or cuisine; less likely if people want specific restaurants.

Essentially, they've looked at the food delivery market as thousands of individual orders all going through individual phone calls or web orders and said, if I could take a percentage of all that, I'd have a great business.