Colonialism also plays a role in the rise of English in music. While it might not be the first factor that comes to mind, it is indeed a factor. England had numerous colonies around the world, such as India and South Africa, which still speak English today even though they are no longer colonies. English was originally enforced in those colonies as a means of oppression, and as part of a civilizing mission. Indigenous languages were considered inferior an uncivilized, whereas English was seen as superior and civilized.
As time went, on, English often took predominance over the native languages in the countries. Though the native languages are still spoken used commonly, English is now a global language so it holds more power since it allows you to communicate with the rest of the world more easily, which thus motivates more people within the country to speak it. This trend can be traced to music, which, as we can see, more artists are choosing to sing entirely in English or partly in English, instead of their native languages. In some ways, English is acting as a colonizing language as it is slowly pushing out native languages. While English in music might seem like a mere trend, it does have deeper and underlying meaning.
Articles:
https://en.wikipedia.org/wiki/Linguistic_imperialism
https://www.britishcouncil.org/voices-magazine/english-form-linguistic-imperialism
https://www.theguardian.com/education/2012/mar/13/linguistic-imperialism-english-language-teaching
http://www.tandfonline.com/doi/pdf/10.1080/01434639708666317