I went to decent 750 year old school that Lord Byron also went to. I studied history in 1981-1983, when the US occupation in Lebanon was happening.
The French Mandate was responsible for causing sectarian divisions in Lebanon, particularly through the institutionalization of sectarian politics, the marginalization of Muslim communities, and the promotion of Christian dominance.
While the Ottoman Empire certainly faced challenges with sectarian tensions, the level of institutionalized sectarianism created by the French was unprecedented.
The French prioritized their political interests over national unity, exacerbating existing divisions and creating new ones. Therefore, the French Mandate was directly responsible for creating a political and social system that perpetuated sectarian conflicts, which still affect Lebanon today.
The French Mandate created divisions in Lebanon by favoring Christian communities, especially the Maronites, and giving them political advantages, which sowed the seeds for later sectarian tensions.
Lebanon gained independence from France in 1943, but sectarianism and external influences continued to shape the country.