It was absolutely a revolution.

The relevant definition of revolution: “a dramatic and wide-reaching change in conditions, attitudes, or operation.”

It didn’t matter if the technology already existed, hardly anyone was using it. Capacitive touchscreens existed, but there was no dramatic change, they were just used in the same way as resistive touchscreens. It was a different way of building a touchscreen, but very much an evolutionary change.

The iPhone was a revolution because it caused a dramatic and almost overnight change in the industry. What techies usually fail to see it that technology doesn’t matter. What matters is how it is used and what it allows people to do.