There are more English speakers globally than there are Mandarin speakers. The number of people that can comprehend some reasonable amount of English is even higher. The Mandarin number is going to contract as China's population declines, the English speaking population will continue to expand perpetually. By comparison, half of the EU can speak English, and that figure is climbing. Less than 1% of the EU can speak Mandarin. The same premise holds for Africa and Latin America. In Latin America, Mandarin is such a rarely known language it's difficult to even measure its use against Spanish, Portuguese and English.

Few people in the rest of the world are attempting to learn Mandarin, because it's a very difficult language to learn and it has a limited cultural projection. The use case to learn Mandarin is primarily restricted to a subset of a subset of business. More people speak English in Asia outside of China, than speak Mandarin.