First, I have to gently correct your question about European improvements of Africa. On balance, European colonization of Africa drove those countries backwards. Research by Acemoglu et al tends to show that the African countries ended up with worse institutions after colonization than before the colonizers arrived! It's not coincindence that some of the best-performing African nations now, like Botswana, were some of the least exposed to European exploitation.

That doesn't mean Europeans didn't try to improve Africa. There were plenty of well-intended efforts alongside the exploitation and simple mistakes. And simple things like "having a population that speaks English" can be an advantage in today's world -- it's not like nothing the Europeans did was useful. But as far as we can tell, the European attempts to improve Africa failed: overall they made things worse for the population, not better.

But after the two World Wars, the world's military order changed. The superpowers were no longer European colonizers like Great Britain, France and Germany, but the Russian-led Communist Soviet Union and the United States of America.

The Americans and the Russians agreed on very little -- but they both despised colonies. The Americans thought of self-determination as something like a universal right; the Russians saw colonization as another means by which rich capitalists exploited poor workers. So the Russians were happy to lend money and weapons to would-be revolutionaries in colonies, while the Americans pressured the colonizers to let their colonies go free.

Caught between the Americans and the Russians, the European colonial powers became less willing to fight local Africans who wanted independence. (With some important exceptions: France fought hard for Algeria, where over a million Pied-Noirs of French descent resided. And Portugal, under its dictator Salazar, refused to let Angola or Mozambique go until his death in 1974.)

To sum up: One, the Europeans didn't improve Africa, although they didn't realize they were making things worse. Two, after WW2 the world's two military superpowers were both anti-colony, which made fighting to keep colonies much less affordable.

(On the impact of European colonization efforts on Africa's economy, I recommend Acemoglu & Robinson, "Why is Africa Poor?", 2010.)

I can't speak to the second question but I'd be happy to provide my own insight to the first part of your question.

My research has predominantly explored one organization, the Alliance Israelite Universelle and their schools in North Africa and specifically Morocco, as part of Mission Civilisatrice or "civilizing mission". The ideology of Civilizing Mission, which became formal and institutionalized policy for France and other colonial powers in the late 19th century, was the idea that European powers were no longer taking territory to benefit themselves, but rather they had a moral obligation to colonize and improve the quality of life of the people they had colonized. They had a mission to civilize and make better the lives of people they viewed as living as barbarians. Thus, the perception that the colonizing influence was positive was absolutely essential for colonial powers going into the 20th century.

Civilizing Mission often entailed the following characteristics: removal of practices seen as inimical to the goals of "civilization", the creation of infrastructure, and moralizing rhetoric. Of the process, one French general had the following to say:

We can legitimately hope to witness… the advancement of the native populations to a higher state of civilization. But such a result cannot merely be decreed; it can only be the end product of a series of patient and converging efforts whose goal is the moral and material improvement of the native through the maintenance of peace and security, the opening of communications, medical assistance and hygiene, the diffusion of elementary and professional instruction, the development of agricultural production and, last but not least, the guaranteed enjoyment of individual rights and of the most sacred right of all- that of individual freedom.

Jews were often the emphasis of civilizing programs in the Middle East. In Algeria, early colonial efforts focused on Jews because they were believed to be more easily modernized in comparison to the Muslim population. This led to the construction of infrastructure, such as hospitals and schools, as well as the advancement of Jewish political bodies with the intent of enacting French colonial plans. Algerian Jews, however, often managed to leverage that position to inhibit certain colonial practices and emphasize others, playing at once both the "colonizer and the colonized".

The goal of the Alliance Israelite Universelle (AIU), which is the topic of my own research, was to bring about the "moral, political, and economic regeneration" of the global Jewish people and to establish a global sense of Jewish brotherhood. AIU activity spanned from Bulgaria to China to Morocco and in general their goal was to help modernize the Jewish people and protect them from persecution.

The primary way that the AIU realized this was through education. Schools were established throughout the Middle East and North Africa. It was believed that through education, the Jewish people could be revitalized and prepared for a new generation of global consciousness and to bring them out of the indolence they had fallen into because of their proximity to their Muslim neighbors. Moreover, the AIU made sure to publish a bulletin annually and semi-annually in the attempt to notify Jews worldwide about the condition of their coreligionists and ask for further support.

The schools themselves functioned as academic environments for teaching subjects like math, science, and history, but had an increased emphasis on learning French, a civilized language, and Hebrew because of its importance to the Jewish people. The schools had an equal emphasis on teaching Jewish students to act "modern" and "civilized" which meant learning French customs, manners, and styles of dress. This was their primary means of "moderniz[ing] or improving the lives of the natives". Conduct, hygiene, and dress were used a visual heuristic means of assessing the relative "civilization" of a group of people and thus these characteristics were often as important as the students learning academic content.

For example, with the introduction of the AIU, poor children were seen to be given a second chance at escaping the socioeconomic hierarchy they were born into. In Morocco, women were now given the opportunity to leave their homes and become educated and pursue careers as teachers at home and abroad. Moreover, the AIU fought especially hard to eliminate the practice of child marriage which it saw as an example of extreme barbarity and backwardness in the North African Jewish population. Child marriage stood in opposition to education since young mothers made poor students and as well as in opposition to hygiene since early pregnancies were extremely dangerous for both mother and child, and often led to mothers who neglected their children.

Thus, in their eyes, they were improving their students' lives by removing the inimical effects of their years cohabiting with Muslims such as persecution, indolence, ignorance, and poverty and introducing to them to the "light of civilization". For the AIU, education and the creation of schools was the best way to achieve these goals.

To answer your question then, European powers instituted education, infrastructure, and removed those bodies of social practice they saw as enemies to "civilization". The degree to which any of this was actually beneficial is, of course, up for debate, and is outside of my place to judge as a historian.

Sources and further reading:

Joshua Schreier, Arabs of the Jewish Faith, the Civilizing Mission in Colonial Algeria (New Brunswick: Rutgers University Press, 2010)

Alice Conklin, A Mission to Civilize: The Republican Idea of Empire in France and West Africa, 1895-1930 (Stanford: Stanford University Press, 1997)

Aron Rodrigue, French Jews, Turkish Jews: the Alliance Israélite Universelle and the Politics of Jewish Schooling in Turkey, 1860-1925 (Bloomington: Indiana University Press, 1990)

André Chouraqui, Cent ans d’histoire. L’Alliance israélite universelle et la renaissance juive contemporaine : 1860-1960 (Paris: Presses Universitaires de France, 1965)

The Bulletins of the Alliance Israelite Universelle