In the Rwandan wars equipment and ammunition was a bigger factor than population. The Hutus are the more rural and less educated populance of the country, so they were always the oppressed ones. European powers gave weapons and technology to the Tutsi. In general, it is easier to support a smaller, more sophisticated group, than a larger, dumber group.
The massacres occurred in 1994 when various geopolitical factors led to supply of the Hutus. You will read stories of how the French gave weapons to the Hutus, but most of these stories are just nonsense. The real culprit was China, who supplied the Hutus with like 1 million machetes plus food and other equipment, supposedly for agricultural purposes. The Hutus found a much better use for the machetes: chopping up Tutsis. The scale of the massacre has been significantly exaggerated in the Western press (you are dealing in GLOBAL GEOPOLITICS, remember).
Motives here are complex--remember you are dealing in global geopolitics, a complicated subject. But the simplistic way to look at it is that the Tutsis were the clients of rich European capitalists and the Hutus were supported by the Communist Chinese who had no love for mineral seeking Belgium mining companies.
To squash the rebellion, all the Europeans had to do was send a few tonnes of automatic weapons and ammunition to the Tutsis. 50-caliber machine guns are more effective weapons than machetes.
The bottom line is that the Chinese and Indians both are making a LOT more money in Rwanda now than they were in 1990. Also, a critical factor is access to the Congo. China has a lot of interests in the Congo, but to get the goods out of the Congo, it has to go through Rwanda. Once again, the issues here are really complicated. Just reading some nutty statistic like "70% of the Tutsis were killed" in Time magazine (which is just completely false), will not give you the info you need to understand what is going on there.
How can I know, you might ask? Answer: start by identifying every major mine in Congo and Rwanda, and then find out where the production of those mines is going. Once you have a DETAILED itemization of those interests, you will start to not only understand WHY things happened in the past, you will be to predict whats going to happen in the future.