Intellectual laziness and stupidty, a religion full of teachings and morality and some idiots try to project (wrongfully legally and historicaly) modern day norms on a lifestyle that was completely different back then because God forbid they learn about the actual religion or actually debate its teachings. Newsflash, everyone married back then as soon as possible, your ancestors and mine did because they lived incredibly short and turbulent lives and they had no schools, social media, basements or anything that implied a long life or encouraging late adulthood. They worked as soon as they were able and they grew up because they had to. The Prophet himself married after his wife Khadija (45 years old) many wives, some were widows, others were relatives of his closest companions and some were political. Aisha herself was bethroed before (like everyone else in her time) to another man and the Prophet only married her because she was the daughter of his closest friend and companion and because it he was officially asked, that's about it. It's not a mandatory age range, a suggestion or even a commentary, most Muslim countries this day and age have set marriage laws that are the same as everywhere elsw ranging from 16 to 18.