I think your observations on the 3 changes in how we communicate are accurate. They are a significant portion of the "how" this has all come to be.

As to some thoughts on the "why", I will only share a limited amount. (don't wish to create too much outrage)

Any person with even a passing knowledge of the rise of Nazism, and/or the consolation of power by Stalinism, is well aware of the disconnect between truth, reality, and language that were features of their rule.
Hannah Arendt pointed out that language was the prepatory path and precursor from gaining and consolidating power to deeds themselves. Performance turned into actuality.
My opinion is that such a path for a very few is pre-planned. For the average authoritarian who yearns for dictatorial powers it is simply a road that inevitably ensues. They create their own emergent outcomes; with each escalation in violence leading to another, greater level.

When I was a boy one of my brothers and i dismantled a some rifle shells we found in a field. We wanted the gunpowder to make our own little cannon. Our father found our stash of powder and had a fit. He informed us we had enough there to turn us into ground meat. I don't know if it was true, but the deeper point was that we were playing with a substance with power we didn't understand.
I worry that the rhetoric, the outright lying, the acceptance of illusion rather than reality is viewed by many as performative play. The reality of it may surprise them.