Video gaming as an industry got bigger. Niche genres like adventure and RTS died out, and AAA titles with inflated budgets in the hundreds of millions of dollars began to be produced.
Now companies like EA are saying a game needs 5 million sales to be able to live.
When indies in any field succeed, the people with money note this, and move in. It has happened repeatedly in the past: films, radio, records, television production, etc. The Industry takes over, sees what sells best--which is usually done along with the assumption that nothing must change; success is simply repeatable, where change can lead to loss of sales. So the indies made all sorts of things on small budgets with a wild, varied bunch of notions, and then industry came along, upped the graphics, brought in big name voices, and grabbed all the programming talent. Which was promptly told what kind of game they would produce.
There are a ton of factual stories that could be told about this. I'll throw in one, deleting the names: four guys who were doctors up in a Canadian province loved playing AD&D over the cold, long winters. They learned programming skills to produce a game that would show their enthusiasm. This game was knocked about through three separate publishers, since they couldn't get it produced on time, but it was a huge success when it finally arrived. And so was its followup. And then the suits moved in, and what they produced became a formula. Three of the doctors sold their stock and moved on. Eventually, years later, so did the fourth. The name of the company is still the same, but it's run by Industry suits who have no interest in games--only in the bottom line of how much expenditures and revenues are realized.
Fortunately, indies have begun to take root, again. Programmers have begun to realize that there's a good economic model for selling successfully on the Web. You won't end up making millions, but you will end up developing what you like, and making a living. Which to some, is worth more than selling yourself and your soul.