I think it is quite simple. Not only Riot but from what we have heard so far, even team owners seem to be in favor of bo1s. I am not going to try to analyze the business side of this deal other than say that it is quite reasonable to conclude based on what we know that bo1s seem to be more profitable for the involved parties. It is also a huge step up for lower tier teams that would want more exposure.

As far as competitiveness goes, I think it is hardly an argument. Bo3s is simply a superior format. However, it does seem that Riot has concluded that the trade off is worth it. A less competitive region with a stronger viewership. Especially when I don't think Korea is going to get dethroned. They do drop games especially bo1s. But there is nothing that indicates that non-Korean teams are able to be seriously competitive in a bo5. If anything, I think it has gotten worse with time. In season 3 and 4.. Korea did have teams that struggled. Meanwhile, season 5 and 6 the top 3 teams at worlds were arguably all Korean. If anything, the 4th best team in world in season 6 was probably KT which couldn't even attend.