Windows 9x had a win 16 subsystem. You could ostensibly access it through ActiveX which was in IE at the time. Certainly more of a hack than an emulator.
It also could have been an Adobe flash imitation which is probably more likely.
Had to have been that given the age. The only other alternative is a binary plug-in.
JavaScript/VBScript didn't have enough control to pull it off and Java was way too slow back then. It used to be a real dog - probably still carries some of that baggage albeit undeservedly (Android for instance, runs things just fine)
It also could have been an Adobe flash imitation which is probably more likely.