I think Fortnite Betting is too impossible. It is simply just a rip-off from many shooting games such as CSGO and PUBG, only made different by planting walls and stairs made from resources on the map. I don't play the game as I found it not that addicting nor strategic at all, especially if you were looking for games that requires a good team play. Hence, I don't see it fit to be bet nor to have a good gambling market.
While some says Fortnite is much better as it's suitable to all age and clearer graphics than Pubg, there are some charts in google that tallies their popularity too but for sure it will depend on what player prefers to play. Betting part will happen when there will be maybe a set of groups or target audience or bettor, they will sure make research whenever that happens as many where into Mobile legends and Dota betting than this 2.
I don't think Fortnite will win in popularity against other games. I guess its not that popular in my country. It sure became popular years ago but no streamers now in my country are still into Fortnite. Dota 2, moblie legends, pubg are the most streamed games here. I don't in any other country as well. Is popularity a need for an esports to really be included in the olympics? Well I think so.
I understand your view point. I must say that the popularity of Fortnite is not that absolute to everyone. Some really likes it, some do not. But I do agree that Esports should be taken into consideration on being part of the Olympics or some huge competition since during this "new normal" people are much inclined with online activities. However, when it comes to betting, I think that the Esports game involve should be popular and being participated by the many. As mentioned, Mobile Legends and Dota are some examples of popular games worldwide.