The idea of belt drive is very old. Probably the oldest drivetrain, actually. And hugely inefficient as it slipped. The toothed belt was much more recent, and was first used on camshafts and other lighter-duty applications. They were made possible by advances in kevlar and nylon manufacturing (though there are other materials being used now, I'm sure).

Harley were the ones who got the idea to try the huge ones for final drive to quiet the noise down. This is a company that does 3-D sound modelling of all new products to make sure they sound right. No one else would have cared so much about the noise from a chain.