What does this mean?

"Even the Catholic Church of the Middle Ages was tolerant by modern
standards. Part of the reason for this was that in the past no government
had the power to keep its citizens under constant surveillance. The
invention of print, however, made it easier to manipulate public opinion,
and the film and the radio carried the process further. With the
development of television, and the technical advance which made it
possible to receive and transmit simultaneously on the same instrument,
private life came to an end."