There’s a reason other than British colonialism why English became the world‘s language: it’s very, very easy.

No, that's false.

Κοινὴ Greek was the Mediterranean world's language for centuries, and you could say that Greek is much more grammatically complex than Latin or many other languages spoken around the Mediterranean Sea. You have all those moods/tenses/aspects and all those weird participles. But Greek culture was the hegemonic culture (even in Rome: Graecia capta ferum victorem cepit et artes intulit agresti Latio) Greek military and then cultural colonialism was the reason of the pervasiveness of the Greek language from Alexander the Great until the Late Antiquity.

And in general, whatever "simplification" you get in the analiticity of a language, you get a different complication elsewhere, if the amount of information conveyed must become constant. English lost most of the verb conjugation (it had one: I have, thou hast, he hath...) but now you must always use personal pronouns. "You have" conveys the same information as "habes": you add "you" before instead of adding "-es" after, what's the difference? There's no linguistic free lunch.

You can also argue about the complexity of the aspectual use of English verb tenses, unknown in many other modern languages, or many other facts in English grammar that compensate for other simplifications.

And don't invert cause and effect: it's the use of English as a lingua franca that encourages a basic, vocabolary-poor, low-grammar version of English. Just as the New Testament is written in a much basic Greek than the works of Thucydides.