Plausibly quite true. But given (1) how often the succession turned violent after a monarch died, and (2) how very little power the average person had - I'd say such prayers were entirely reasonable. If they made "life in the lower 99%" just 1% more bearable, that'd be a worthwhile RoI.
Demon-Haunted World is a book worth reading...but Carl often seems to forget that 99% of humans are neither huge science geeks (as he is), nor rationalist robots.