Why was there such a strong hate for Catholicism in the leaders of the Revolution?

There was strong hate for Catholicism in the leaders of the Revolution because the Catholic Church represented what they hated. At that time, the leaders of Revolution were against the leadership and monarchy at the time. The aristocracy, the rich and the powerful had long been Catholics.

They were from the first two estate of the French society (clergy and nobility), they were exempted from tax and the third estate had to pay a direct tax called “taille”, they had to render free services to lords. The clergy and nobility did nothing and got everything from the commoners.

The commoners also paid another tax known as “tithe” to the clergy. The clergy enjoyed monopoly on religion which they abused. It was only natural for the leaders of the revolution to hate the Catholic Church that had great power in France.

War is usually caused by a belief in insufficient power and share of assets/money. It is difficult to answer this question when you have not specified which revolution (of many thousands) or even which country. I shall have to guess but remember, most people think internationally.

Catholics have been central in many serious conflicts. If you are from the US I assume you refer to the American Revolution of 1775–83. Catholics were indeed unpopular. This originated from the arrival of British Protestants to the American colonies.

The Catholic/Protestant divide in Britain was endemic and those attitudes were brought to the US alongside the chest of clothes and the bible. Every state except Pennsylvania had some anti-Catholic law such as preventing them from holding public office, from voting, practicing law, or worshipping in public.

There have always been huge riches in the Catholic church and this, together with the massive followings in South American countries, induces insecurity amongst Protestants.