In 1968, my friend Brown Carpenter and I went to a George Wallace presidential rally in Norfolk, Virginia. Maybe 10,000 people half-filled a football stadium, where we were warmed up by the singing duo of Mona and Lisa (fo' real).
After not too long under a hot sun, Wallace climbed the stage (this was before he was shot) and gave his standard stump speech. It was well received. A young girl in front of us sighed, as after coitus, "Thank God for George Wallace." But the reaction was merely favorable, not wild.
Except when a television crew would point its camera at a section of the stands. That section then erupted in a violent demonstration. The sections on either side watched quietly, and as soon as the camera turned away the noisy section settled back into something close to torpor.
The television coverage that evening thus gave a misleading impression of what had occurred.
In those days, teevee cameras were not so common, and while there were home movie cameras available, they were not convenient and the film was expensive. Not every public or semipublic event was recorded by several different people.
Now, we expect to have at least grainy surveillance footage of almost anything. The results can be interesting. Click through also to the Bloomberg example of Cruz in front of a rightwing crowd.