But normal game companies? Especially casual game companies? Do people really have that much faith that Candy Crush and the like is more than a generation's flash in the pan like Tetris, Pogs, or Tamagotchis?
No, but people have faith (quite often irrationally so) in their own ability to time the market, and be able to exit at the right time.
Activision and EA are movie studios. Zynga is a casino. Activision and EA want big hits and loyal fans. Zynga doesn't really care if you've played any of its previous games, or whether you play games at all; it just cares whether you'll play right now. (And maybe later, and later, and then more after that.)
(Of course, casinos also have their whales, as do Zynga-style games.)
It's such a tough business given that you need to invest in building a full game before you really know if it's going to be a hit. You could put out concept art, etc. but I'd argue that you can't really do "private betas" like what we do with SAAS just yet.
When the game got into a playable state he already got some followers. And the word started to spread. It was still a free Java applet at the time. Then people started to play it on Youtube and it exploded. And that's when he started charging 10 bucks for the game.
Whatever you may think about PES, FIFA was forced to evolve a lot to compete with it (everyone used to think PES was better). Progress has been more modest for Madden, which has had no competition for something like a decade.
This makes them a safer bet than companies like King or Zynga, which bet the farm on one particular quadrant of the overall gaming universe (casual games on mobile devices). If the world stopped playing games on their phone tomorrow, EA could survive that.