This is a more interesting discussion than the rest of the thread, so indulge me while I glom onto your post and analyze it.
Blizzard is a bit of a strange beast in this day and age. They have an extremely strong brand in the PC community - to the point where I know people who will buy anything and everything that they produce. “WoW? Yes please. Hearthstone? Of course! Overwatch? Well, it’s a FPS that’s nothing like any of their previous games and I don’t even play FPS games, but heck yeah! It’s a Blizzard game!” This is a PC gaming company that doesn’t sell through Steam, and instead makes you use their own wonky proprietary system, with their own proprietary online service to play online. They released Diablo III in a broken state, with a huge “pay to win” incentive and an online auction house that they could tax with real money in order to bilk more money out of their full retail purchase. They are selling people a collectible card game that doesn’t even have cards, using the F2P model. And they are beloved.
Forget for a minute how they got such loyalty and whether they deserve it. That’s a fascinating but separate discussion. The point is they have a super strong brand. So Blizzcon reinforces that brand a lot better than, say “KI World Cup” reinforces Microsoft’s brand, or any major tournament like CEO (before anyone jumps down my throat - I’m not suggesting MS shouldn’t sponsor tournaments. Just walk with me here…).
Blizzcon is also a convention. It has show floor, and presentations and all kinds of stuff for Blizzard to showcase their future products (and other peoples’) to their adoring fans. The primary audience is fans - not competitors. They charge $200 a ticket, just to get in. It’s four per family and they are sold out. CEO charges $30 to people not playing games and $50 to people competing. The primary audience for CEO, and other fighting game tournaments is people who are actually competing. Plus whoever they bring with them (mom, dad, girlfriend, boyfriend, kids). Blizzcon is actually SELLING stream service. Let that sink in. You have to pay to watch it on your PC.
But the real reason I expect Blizzard is making money, not spending it, at Blizzcon is sponsorships. Now every fighting game tournament has a sponsor, from the local Arby’s to MadCatz to Microsoft. But the trick is not getting a few T-shirts or a free game download as a prize, it’s getting real money from people to advertise. Blizzcon had about 25,000 attendees last year - all devoted PC gamers (and some simple math tells you that’s $5,000,000 they collect at the gate). So guess who one of the sponsors was? Windows 10. It’s worth it to put your logo on stuff that 25,000 fans will associate with their good time, and then get it in front of all the folks watching on stream etc. If that audience is tailor made for your product, all the better. CEO has sponsorships. They have really good ones, with lots of companies that make fighting game related products. And I’m certain they are using that money, or those donated items to the best of their ability. But they aren’t able to get the kind of money from those sponsors that Blizzard is able to get for Blizzcon. Why? 25,000 fans is why.
As @TheKeits and others pointed out - the fans come first and then the sponsors follow. Blizzard didn’t just wake up one morning and say “hey look, 100 people are having a Warcraft tournament. Let’s give them $1,000,000!” KI tournaments are great, but they are advertising KI. KI doesn’t have the budget to swing around to drop a money bomb on CEO. The audience (of maybe a couple of thousand people on a live stream?) isn’t big, nor is it likely to be a target for MS’s big products (like Win 10). So the economics matter. And you can’t just bring up “Company X does this thing, why can’t Company Y?” Because the situations aren’t really comparable. It makes much more sense for MS to sponsor Blizzcon than to sponsor a pot bonus for a KI tournament.
TL:DR - Blizzard already has millions of fans glued to Blizzcon. So they can get people to give them money and use some of it for prize pools. KI is awesome, but it just doesn’t have anything like the numbers those Blizzard games pull.
Which brings me back to something else. I don’t want to doom the community with low expectations, but I just don’t think it’s realistic to think that KI is going to rocket into the stratosphere and be the next League of Legends.