In reality, changes in laws happen when a small group supports them and, small opposition notwithstanding, vast majority of people do not care. One of the easiest ways to make the majority care - and oppose you - is to push your changes in a way that violates existing legal framework, particularly important things like a constitution. As long as you don't do that - as long as you take things slow and don't raise people's alarms - you can boil the proverbial frog.
That's what these clauses are meant to protect from. A series moves, planned or accidental, that could turn the country into dictatorship.
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[0] - I.e. the kind that's valid as long as enough people believe enough other people believe it's valid. Like a constitution. Or money.
You cannot simply write down a law prohibiting becoming a dictatorship and then sit back thinking all will be fine, because then these groups will simply grow their power until they can ignore the bits of the law they don't like. And they don't need to change the law to gain power, they merely need acceptance of their telling of events.
On the other hand, without extensive support you cannot create a dictatorship because that word implies such extensive societal control that there simply must be extensive power behind it for it to function at all.
But my point was mainly around popular movements. Not going to comment on international judgement in these circumstances
The Third Republic had actually lasted quite a while. There was definitely a mess before that: monarchy, revolution that created a republic that turned into an empire, then a monarchy again, then a republic again, then the nephew of the original emperor being declared emperor... the 19th century was not a good time to be French. (And I'm leaving out some revolutions and constitutions that didn't go anywhere.)
But after that they really had settled down, until an outside force blew it all up. The 19th century wasn't really all that solid anywhere in Europe. Germany and Italy didn't do any better.