Have a Punderful Day!
Well, firstly, it is very important to understand that times were quite different then, 1400 years ago. Getting married when you hit puberty was the norm, in most parts of the world, and even sometimes today. Young girls who were physically mature were not considered young girls, rather, young adults. Second of all, it was definitely not a marriage that came out of lust, physical desires. Muhammad (pbuh) married Aisha (ra) on suggestion. Actually, most of his other wives were much older then him, they were widows, divorcees, or woman who proposed to him themselves. Also, Aisha (ra) never showed any displeasure to the marriage. The consent of her, and her parents, was given. Finally, Aisha (ra) led a very happy life with him. They both enjoyed each other's company very much, and Muhammad (pbuh) always held her in very high regard. Hope this answers your question.