Omollo,
If it were just about fear of Tutsi take-over, then Nkurunziza is even crazier than I thought. Aren't Hutus 85% of the population?
How do Hutus lose if Nkurunziza does not run?
Have we forgotten how non Kikuyu Kenyans tolerated Moi on account of the excesses of Kenyatta? Moi was never in danger of losing in elections in Kenya but the fear of military coups was always there.
To answer you however, note that Tutsi's tyrannized over majority hutus by military brute force. Their numbers have never increased in Burundi or Rwanda but they rule Hutus in Rwanda and until Nkurunziza came, they ruled Burundi. So the percentage you mention is meaningless. Tutsi grab power and then apply maximum brutality.
See how Kagame has arrested and kept the leader of the Opposition in prison. I am sure he plans to have her killed inside when the world is not paying attention. Yet he is feted by Blair and others. He presides over a dictatorship.
Somebody said he wants to run for a Third term. What joke? Kagame took power way back in 1994, remained "Vice President" with all the power, dictating to the so called "President". He finally decided to drop the pretence in 2000. Right now he can choose to be a District Officer and he will still rule Rwanda from his district.
2000 - 2003 - Transitional Constitution (like Nkurunziza)
2003 - 2010 - First term
2010 - 2017 - Second Term
2017 - ???