every sport organisation is trying to milk the maximum money they can and thus FIfA is no different then other sport organisations who’re too trying to get maximum money they can from their respective sports eg ICC. Furthermore if FIFA World Cup is held every two year’s then most player’s will quit playing national football as it’ll increase their work load and the excitement of winning the World Cup will end.
I feel like making that much money must be the main reason for any business in the world. They are an "organization" and not a company perse, but the aim is the same, making as much money as possible. When you make it 4 years in between, people wait for it for a long time and the value of the cup increases.
Think about it, you could only play in 4 or 5 tournaments all your career, even if you get elected at 16, which is very rare, 20 years means 36, so 5 is usually the maximum amount anyone could ever join, usually less. But, when you make it 2 years, then it would be like 10, and suddenly all of your waiting is over very quickly and it's not that rare and unique anymore. I think it's quite important to just realize that if possible.