I know exactly how it happened. It's pretty genius. About thirty years ago, I used to listen to a lot of talk radio because I was driving an ancient car (my Dad bought it as the 'kids car')and only the AM stations would pick up. There would be talk show after talk show pushing the "be a better person" agenda. Everybody wants to be good, right? That was the start of virtue signalling and they escalated it a little every year. You do something good, you give yourself a little pat on the back and enjoy the endorphins. People admire your good deeds and ethical behavior. It's addicting. Now they're so addicted to the virtue signalling that they're destroying themselves.