Conversation so far:
What was his religious background?
Buddhist.
Was most of the country also buddhist?
the religious composition at the time estimated the Buddhist majority to be between 70 and 90 percent.
If they were the majority, then why were they being persecuted?
President Diem was a member of the Catholic minority, and pursued discriminatory policies favoring Catholics for public service and military promotions.
How did the people react to this?
Some Buddhist villages converted en masse to receive aid or avoid being forcibly resettled by Diem's regime.
So did Catholics then become the majority?
The Roman Catholic Church was the largest landowner in the country and enjoyed special exemptions in property acquisition.
Is there anything else interesting from this article?
Buddhist discontent erupted following a ban in early May on flying the Buddhist flag in Hue on Vesak, the birthday of Gautama Buddha.
Did they protest or do anything to fight the ban?
A large crowd of Buddhists protested the ban, defying the government by flying Buddhist flags on the Buddhist holy day of Vesak and marching on the government broadcasting station.

Question: What happened to them when they protested?
Self-contained rewrite: What happened to the large crowd of Buddhists in Thích Quảng Đức's country  when they protested?