It's a very hard language with a complex written form. There are likely hard upper bounds to its worldwide popularity.
Look at Russian. Even when the USSR was the most fashionable country on Earth, when Western intelligentsia (eh) was massively convinced that Russians were showing us the future, people were not queuing up to learn Russian. Often Russian intellectuals had to speak another language to communicate with the "outside" (when they were allowed to). It was simply too different in its alphabet, too complicated. The same happened with Japanese, despite Japan being a massive economic and cultural power for more than 40 years. Japanese is occasionally fashionable but it will never be a lingua franca.
English might not be the easiest language in the world or the most regular, but it's definitely easier than any Asian language featuring complex glyphs. Its pronounciation rules are relatively easy. Its lineage is markedly European, which keeps it close to French and Spanish and makes it easier to piggyback on their own spread. Even if it were to lose its importance tomorrow, should the US self-nuke or something, chances are that its replacement would still be based on the Latin alphabet. That's what is used in South America, Australia, Europe, and large parts of Africa, regardless of whether they speak English, Spanish, French... So that's what will likely continue to be entrenched, one way or the other. Chinese will grow in importance for sure, particularly in Asia, but it will never be "the" global language.
There's a joke that the most common language in the world is bad English. I have a theory that the diversity of English speakers makes it more forgiving of pronunciation, word order, and tonal mistakes than languages with fewer speakers.
Chinese is popular regionally in Asia and among diaspora, but it doesn't have the anywhere near the number of outsiders trying to learn the language to tap into the social/cultural system as English does.
English is effectively half-French, like French was half-Latin, which in turn was half-Greek. Europeans basically moved from a language to its immediate cousin, for more than 2000 years.
Han might be half-something too but it's definitely not something anybody ever spoke in Europe, South-America, or Africa. Europeans will likely never speak Chinese in numbers comparable to modern-day English.
Look at Russian. Even when the USSR was the most fashionable country on Earth, when Western intelligentsia (eh) was massively convinced that Russians were showing us the future, people were not queuing up to learn Russian. Often Russian intellectuals had to speak another language to communicate with the "outside" (when they were allowed to). It was simply too different in its alphabet, too complicated. The same happened with Japanese, despite Japan being a massive economic and cultural power for more than 40 years. Japanese is occasionally fashionable but it will never be a lingua franca.
English might not be the easiest language in the world or the most regular, but it's definitely easier than any Asian language featuring complex glyphs. Its pronounciation rules are relatively easy. Its lineage is markedly European, which keeps it close to French and Spanish and makes it easier to piggyback on their own spread. Even if it were to lose its importance tomorrow, should the US self-nuke or something, chances are that its replacement would still be based on the Latin alphabet. That's what is used in South America, Australia, Europe, and large parts of Africa, regardless of whether they speak English, Spanish, French... So that's what will likely continue to be entrenched, one way or the other. Chinese will grow in importance for sure, particularly in Asia, but it will never be "the" global language.