Football (the folks over the pond tend to call soccer ) is without doubt the most popular sport and the World Cup is obviously the most watched sporting event worldwide so the sportsbetting industry gets a lot of business during such international competitions. The public interest is so high that even people who don't usually bet or don't watch much sports have a punt or two just for fun. E-sports on the other hand is a niche business and its general public is mainly teenagers who play PC games whereas whole nations care about their national football teams. They are not exactly comparable in my opinion.