I guess you don’t know how Motorsport works.
The sponsors are not busy with retaining the money, actually they don’t even want that money. What they are busy with is advertising their brands. Whenever a car brand emerge champion at any World Rally Champions they tend to sell more cars during that year going forward.
This competition gives buyers confidence on the type of the car they should buy, the durability, it’s adaptability to terrain, its speed among many other things.
Other sponsors also just look for visibility of their brand.