Rwanda has the role that Zaire used to have in the cold war by controling neighboring countries. Zaire was behind those coups who put Museveni & Habyarimana on power in Uganda and Rwanda. The army of Zaire even helped Habyarimana to stay in power by figthing against Kagame's FPR, forcing them to return back to their base in Uganda. Mobutu also financed and military supported UNITA and FLNA in Angola. Zaire didn't profit from the money USA gave them and their minerals because Mobutu killed the economy with the Zairisation and was only letting his family, clan and the political elite profit from it, also the huge corruption was putting the economy more and more down.
About musicians like Fally,Werrason,etc. not being rich has nothing to do with the politics. Its all about Soneca/Socoda, those tv, bars, radio channel not paying the taxes and piracy being very strong and those people doing being protected. If all that stuff was fixed than they would have been rich like artists coming from Ghana and Nigeria who are protected by the governement and being forced to do matolo, selling songs to donors, touring months long in Europe to survive.
Don't forget that Rwanda is just smal country. Its just the half of the Kongo Central-province, so with the money they make with all minerals coming from Nord Kivu, South Kivu, Maniema and the Ituri-province its very easy to develop their countries.
Dr Congo is to big. The federalism is a better way to govern the country, like Germany, USA, Russia and Nigeria, instead of a central governement in Kinshasa. Because those politicians don't cares what happens in the Equateur-region, Bandundu, province-Oriental and Kasai. They only focus on Kinshasa, Kongo Central and Haut Katanga. But some people are against federalisme because they fear that it can split the country in the future like Yugoslavia. Tshombe and Kasa Vubu were working on a constitution that had to bring federalism in Dr Congo to govern the country after years of war, back in 1964 with "La Constitution de Luluabourg", with the 6 province having a kind of autonomy and Kananga (then called Lualuabourg) having to become the new capital. But the coup of Mobutu blocked it and Mobutu himself was against federalism.