[pzs]

It took the diamond industry several decades (and huge investments) to build their carefully crafted public image that translates into diamond purchases nowadays. These efforts are still in progress today. I am not sure if there are similar powers and interests behind the moissanite industry to match that.

There appears to be some cultural change happening around smoking. It is very slow despite the proven causal relationship between smoking and lung cancer. The tobacco industry is working hard to ensure they can continue to operate and transition to products that are (at least perceived to be) less harmful to people. However, the speed of this change does not appear to be driven by the severity of lung cancer threat, but by the lobbying power of the tobacco industry that ensures they don't go out of business while the transition is happening.

[RandomLensman]

It is probably true as far as retail engagement rings and certain smaller jewelry etc. is concerned, but rich and powerful people liked and valued diamonds way before that long marketing campaign.