She was not mentally mature, it was said she was playing with dolls when her mother grabbed her and washed her face and hair. Does that sound like a mature person to you?
Honestly does a person who his fully matured mentally play with dolls and need their mum to wash them? Or is this the actions of a child?
Also, because this was allowed, countless children have died from this, Just because you have a period does not mean you can bear pregnancy. A period happens when the body begins releasing eggs, it can start before the pelvic bones have grown large enough to fit a baby head through. As a result, you can get pregnant at this age but child birth is sure to kill you. That is why many child brides died from delivery, it is a painful way to die, Allah knew this would harm many children and did still allowed it, we did not realise the dangers of such practices until a few hundred years ago when our understanding of the human body improved.
Also, children do not have a uterus that is thick enough to withstand the thrusts of a penis. This matters because again you are allowed to marry as long as the person has hit puberty, this can happen to a child and when the marriage is consummated the penis of an adult can pass the cervix and push on the cells of the epithelium and endothelium cells of the inside of the uterus and cause it to tear consequently causing the child to die either of imminent infection or extreme blood loss.
-Again ask yourself, Allah knew that many children would die from having sex and that this would become common practice in many parts of the world, yet he still allowed it once again causing many children to die, it was not until recently we understood this is dammaging to children and needs to be outlawed. God allowed something incredibly dangerous to children who do not have adequate understanding of the matter, why?
The point I am making is this, God could have chosen an age where the body can actually withstand Penetration, an age where most girls would not die from sex or child birth, it could have been an age for example 20 where everyone could withstand these actions. No instead he chose an age, fully knowing it would cause harm to countless people and required us to advance our understanding of Anatomy and Physiology to determine that this is a harmful practice that should not be done. God was not interested in saving those children from a perfectly avoidable situation, instead he wants us to determine the risk and then say "even though this is halal it is a terrible idea", Tell me, does that sound like an all knowing and caring God who is looking into our best interest and giving rights to children so they can have the liberty of life, or does this sound more like the ideas of an entity without all knowledge or without interest in the well-being of countless innocent children, a practice still practiced today in parts of the world justified by "it is halal".
Notice too I did not mention emotions, nor did I appropriate our morality (that everyone has a right to live), I am just being objective and telling you the consequences of the Marriage of Muhammad and Aisha on people generations after the event. Knowing now the risks of such practice, would you be willing to gamble the life of your daughter who is say 12 years old with me if we were living in Yemen? If so you are a cruel person with little regard for your child, if not, then you understand that while this is allowed and not a command by god, it is something with heavy consequences and little to benefit the person who is risking their life, a marriage that could happen when the bride is older.
This is not about why does Allah allow us to take part in Dangerous activities. No it is about an all knowing God allowing behavior that risks many people's lives at a time when it was not known that this would surely end the life of many children. Not to mention even if this fact was known by people at the time, they are bloody children, they are not old enough to make a decision so important like who do they want to spend the rest of their life with. The brain is only half mature to that of an adult, does that really seem like a good idea to let kids determine their fate? Their mental faculties are no where close to be able to understand risk analysis.