This is an oversimplification but marketing is the driver behind all sales. The industry creates a need/want then creates product to sell fill the demand. If you recall, triples had about come to the end of their life as far as development. Ski Doo came out with the CK-3 chassis that was supposed be a true trail weapon with triple power but it never took off. Polaris laid a complete egg with their triples and the Agressive chassis. Starting with PWC engines didn't help them at all. Cat made good product. However, there weren't a ton of new innovative ideas coming down the pipe in those sleds.
At the same time, snocross and cross country racing was dominating the racing news cycle and people paid attention to that. They wanted the next race sled or at the very least, the technology that was on it.
So, marketing stepped in, told us we all needed big bore twins and the rest is history. Then we needed four stroke, then we needed rider forward, then we needed.... The list goes on.