That's not what they said. "Measured and rational speaking" is usually terrible marketing. It barely works on college-educated adults and certainly doesn't work on the mass market.
The example they gave is Trump in a garbage truck, but that's just one way in which Trump made himself enormously appealing to the non-elite.
They can not even understand that 80% of the country does not talk like a rich, educated liberal. It is so frustrating.
Worse, they don't see that a near-majority of the country is actively put off by someone speaking like a rich, educated liberal.
The #1 exercise Democratic politicians should do over the next 4 years is to spend hours and hours and hours actually listening to working-class people in flyover country and trying to really understand them. They just don't get it yet.