I'm about to break this down for you all so listen carefully because you'll never really see me do this again.
I'm korean and i was born in korea in 1980. I moved to NJ when i was 3, then moved to nyc when i was 8 and ive been here ever since. I did live in korea from 2000-2002 and ive been there a few times from then til now. I have ALWAYS been a gamer. Ive only missed a few days of work/school/social events for the reason of gaming. I was really into nintendo, then Playstation, then i went back from PC and ps2/ps3/ps4 xbox/xbox360 and back to PC now. I've played a ton of WoW, Everquest, LoL, dota, and a shit-ton of other MMOs Mobas FPS's RPG's RTS and all the mainstream games you could think of.
When i went to korea in 2000, i noticed that there were SO many Internet cafes(in korea we call them PC Bangs(PC rooms)) EVERYWHERE. In Seoul, they must have had atleast 1 on everyblock. And this is back in 2000 when online gaming was still relatively new. In the united states, there were probably like 10 in the country if any at all( i have no idea but i know ive only seen 1 in nyc at the time). They also had arcades everywhere. I would really enjoy going to the internet cafes with friends and playing games. 95% of the people in there would be playing starcraft. When they got bored, if they ever got bored, they would play things like rainbow6 or ultima or some onlineMMO(maybe lineage?). SC was simply huge and it was on every PC in korea. Everyone in that country knows what starcraft is like the united states knows what the board game Monopoly is. It was integrated into the life of kids. I used to watch TV and saw that they actually had televised tournaments of starcraft back then. I thought it was amazing. The big corporations started to see that there was actual money to be made. They started to invest in the best players. Players had contracts and advertised for these companies. And this was back in 2000. Imagine Apple or IBM or AT&T, heck, even Disney or Facebook endorsing players in the US. The proper gaming culture is simply not there yet.
The cost of living in korea is less, and the real estate is less. Im sure its way cheaper to manage an internet cafe in korea then in the US. They consistently sell out venues and pack stadiums with esports(mostly starcraft). I havent been there in a while but I still think Starcraft 2 is still bigger than league over there. No one outside of korea will ever come close to beating the best korean players in starcraft2. While starcraft has been around for almost 20years, league is still fairly new. The united states has millions of people playing league but only a handful of people will ever make money from competitive gaming. The US is probably still not even close to where korea was in the year 2000 when it comes to esports. This is where the money comes from but the talent is being brewed in the thousands of internet cafes in korea.
However, i firmly believe that the rest of the world will eventually catch up. When average people compete against the best people and they lose, they gain experience and they will eventually rise to the occasion. But this will take YEARS. LoL is evolving and different strategies form from patch to patch. Its going to take several years because there simply is not enough international play. Teams like TSM or C9 or those EU teams will have to go to korea and i just do not see that happening. My guess is that asian countries will rule LoL for the next 10-20 years. And i say asian because other asian countries also harbor mass amounts of youthful gamers and i understand that they have a similar gaming culture that korea has. And this part is just my opinion and a rather ridiculous one that that, but I also believe that asians have great hand-eye coordination and they are amazing at mathematics(obviously). I know it sounds ridiculous and you may ask, what does math have to do with gaming? Its all about logic and figuring things out. All great gamers are good at math. But not everyone good at math is good at gaming, hand-eye coordination is important as well. Test that theory on anyone good at video games.
NA and EU should only be allowed to bring 2 teams to worlds at this point, in reality, it should be just 1. The difference in the amount of talent across these regions are staggering. You can put the top 8 korean teams in worlds with 2 in each group and they will probably all make it out of groups.
-culture
-financial support
-lifestyle
-brain
not exactly in that order.