Sure it always starts with an individual or a group of individuals, but what you describe is some sort of virality. Like a counter-epidemic if you will. It’s one way of getting changes in culture, which relies a lot on lucky timing. Like the Tee-totaler movement that lead to the prohibition in the US.

I think these events are extraordinarily rare. Civil rights is another one. These only happen when the bad situation is totally unbearable. Like huge wildfires happen when there is forest overgrowth.

Otherwise you need some sort of top down approach. if you want people to actually recycle their trash, fine them if they don’t. if you want people to stop dying on the roads, severely punish DUI and speeding. If you want people to have more children, reduce their taxes if they have some, etc.

Now fixing loneliness is complicated for sure. My opinion is that a grassroot movement is not going to succeed, cause the current situation is not that unsustainable, so people won’t take it in their own hands.