Not quite true...
England: monarchy overthrown 1649, replaced by the Puritan republic of Oliver Cromwell (perhaps not a democrat by today's standards, but certainly one by those of the 17th century); restored 1660 to the virtually unanimous joy of the people
France: monarchy overthrown 1792; restored 1814/15 (sadly, the French didn't learn their lesson)
Greece: monarchy overthrown 1924, restored 1935 (only lasted 39 more years, but still an example that disproves your assertion)
Spain: monarchy overthrown 1931 and replaced by a liberal democratic republic; this led to civil war and the monarchy was eventually restored in 1975 thanks to General Franco, and is quite popular today.
Cambodia: monarchy overthrown 1970, restored 1993
Too bad that your "Democratic Republics" that replace monarchies usually turn into horrific tyrannies: France, Russia, Germany, China, Yugoslavia, Bulgaria, Romania, Albania...were those regimes your idea of "tasting freedom and not turning back"?
Not a single one of those "democracies" have the checks and balances of our Constitution. Of course, the modern European Republics are based on the American model.
"Spain: monarchy overthrown 1931 and replaced by a liberal democratic republic; this led to civil war and the monarchy was eventually restored in 1975 thanks to General Franco, and is quite popular today."
Am no longer impressed with these European monarchs. They will rubberstamp anything that ensures their survival. Their power has gone; most are protestant or worse and I get fed up with them extolling the virues of democracy and poverty! The best monarchs are mythical like King Arthur. They are not weighed down by human failings and the judgments of history.