Hyabarimana and Ntaramirya made a mistake of coming to Tanzania to negotiate with Kagame and Museveni, and trusting that Nyerere and his boys would guarantee their safety, unfortunately not. Their plane was shot down, starting a brutal genocide which churned this region's soil with blood.
Tsishekedi is really wise not to come to Tanzania because his knows his security will not be guaranteed. Most Tanzanian officials, including The Boss Lady and her acolytes have a dangerous and insatiable thirst for money and power, it's really easy to be swayed and sell him out.
There's no diplomacy in Africa. Might Makes Right, and the Weak Suffer. It's Greed, Clientelism and Ignorance that rule supreme.