I will argue that three main historical differences between Eritrea and Rwanda have informed their disparate current political situations. 1) geopolitics differed in pre-colonial Rwanda and Eritrea: whereas the horn of Africa(including modern-day Eritrea) had been dominated for centuries by the kingdom of Abyssynia, in the Great Lakes Region, the pre-colonial Kingdom of Rwanda remained independent from foreign domination up until the point when Rwanda fell under the control of German(1885 to 1919) and the Belgians(1922-1945). 2) On the other hand during the colonial period Eritrea was dominated by Italy which did not engage in the same divide-in conquer strategies as the British and the Belgians. 3) Ultimately, Eritrean identity would be influenced by Diaspora caused by years of war with Ethiopia, while the lingering rifts between Tutsi and Hutu ethnic groups tore the young nation apart.
During the medieval period, the Abyssinian Empire undertook centralization around a national Christian Church and feudal structures, extending its authority to the modern day territory of Eritrea on the Red Sea. The Muslim inhabitants of Eritrea fell under the reign of a Christian monarch, and would only conjure political independence upon the end of World War II. The essential political structure of the kingdom of Rwanda however remained unchanged throughout precolonial, colonial and post-colonial periods: a Tutsi minority elite dominated over the ethnically Hutu masses.
According to Tekeste Negash, an Eritrean author, the Italians aimed to hinder social and economic development of any one ethnic group in Eritrea which could pose a threat to the colonist’s authority. ( Italian Colonialism in Eritrea, 1882-1941: Policies, Praxis and Impact by Tekeste Negash:The International Journal of African Historical Studies ) Nevertheless, Italian colonists inadvertently helped develop a common Eritrean identity, by breaking down the feudal system and fostering in Eritreans, especially those educated in the capitalism Asmara, a sense of political awareness(Giampaol Calchi Novati: Colonialism as State-Maker in the History of the Horn of Africa: Proceedings of the 16th International Conference on Ethiopian Studies). The Belgians saw the existing Tutsi leaders as natural allies, and the Tutsi minority received political and economic patronage from their colonial overlords in exchange for loyalty.
During the struggle for independence from Italy and then from Ethiopia, lasting from 1961 to 1991, a mass exodus of around one million Eritreans occurred, creating one of the largest diaspora communities on earth(Nicole Hirt, ‘The Ertiriean Disapsora and Its Impact on Regime Stability: Responses to UN Sanction’: African Affairs, issue 2014). The development of strong political institutions was thus stalled so that upon the end of war in 1991, there were few balances of checks existing in Eritrean government to prevent Isaias Afwerki and his party from securing a monopoly of power on the government, albeit an unstable one. Upon securing independence from European colonizers, the Hutus saw their chance to secure political rights for themselves and elected Gregoire Hayibanda, thus reversing the political order of Rwanda. (Jean Herman Guey: Renversement du gouvernement de Grégoire Kayibanda). Tensions between the Tutsis and Hutus fermented throughout the 60s, 70s and 8-s, leading to the creation of the Tutsi led Rwandan Patriotic Front who launched a war against the Hutu Government. The Hutus responded by carrying out the largest Genocides in history.