Original: This may have started because many prominent broadcast personalities -- such as Walter Cronkite , Johnny Carson , David Letterman , Tom Brokaw , John Madden , Rush Limbaugh and Casey Kasem -- came from this region and so created this perception .
Simplified: This may have started because many television show hosts -- such as Walter Cronkite , Johnny Carson , David Letterman , Tom Brokaw and Casey Kasem -- came from this area .