Original: The fact that both Louis and Charles ruled by hereditary right rather than popular consent was the first of two triggers for Les Trois Glorieuses, the "Three Glorious Days" of the July Revolution.
Simplified: Both Louis and Charles ruled because of their birth, not because a great number of people wanted them to. This was the first of two things that began Les Trois Glorieuses, the "Three Glorious Days" of the July Revolution.