"You think the French monarchy was overthrown because they didn't try hard enough?"
Yes, actually I do. Are you aware how long the process of transformation was and how little actual violence did the royal troops mete out? Most of the blood during the French Revolution was shed among the revolutionaries themselves, later. Not by the old regime which barely resisted what was happening, being confused more than anything else.
The French monarchy was remarkably limp-wristed in its reaction to the post-1789 developments, probably because, in the beginning, not even the revolutionaries themselves expected to actually dismantle the monarchy. There was no civil war similar to Cromwell's England, nor massacres in the streets similar to modern Iran. In the largest event of that early period which could be called "a battle" (Storming of the Bastille), a grand total of 114 royalist soldiers made their last stand. Which is tiny for a country the size of France.
It took about a year for the situation to progress from the first session of the Estates General to the royal family attempted flight from Versailles, and 2,5 more years for the King to be executed. A classical case of the frog being boiled very slowly. The royal regime was indecisive and offered close to zero violent resistence.
(If you want to learn about an actual abortive French revolution which was suppressed with actual brutal violence by the royalists, look up Fronda of 1648-1653.)
In contrast, current rulers of Iran have 0 doubts about what is going to happen to them - and within minutes - if they get caught by the street crowd that hates them.