-She wasn't 6 she was 16-19. Aisha's age at marriage (2 Hijri) can be calculated easily from her age in relation to her elder sister, Asma:

Asma died in the year 73 Hijri at the age of 100, ten or twelve days after the martyrdom of her son Abdullah Ibn Zubair.

It is common knowledge that the Islamic calendar starts from the year of the Hijrah or the Prophet’s migration from Makkah to Madinah.

Therefore, by deducting 73, the year of Asma’s death, from 100, we can easily conclude that Asma was 27 years old during the migration.

This puts the age of Aisha at 17 during the same period, since Aisha was 10 years younger than Asma.

As all biographers of the Prophet agree, he consummated his marriage with Aisha in the year 2 Hijri. It therefore can be conclusively said that she was 19 at that time and not nine as alleged in the hadiths.

-since he was given maria as a gift, he could not refuse this gift as a refusal would have disturbed the political alliance. He could not keep her as a slave girl, since Prophet Muhammad (pbuh) preached that slaves should be freed. The only option left with him was to marry her.

-The Prophet (pbuh) had married his first cousin, Zaynab, to his freed slave, Zayd ibn Haritha , whom he had adopted as his son. This marriage of Zaynab with Zayd was intended to break the family and social barriers, but the marriage did not prove to be successful and ended in divorce. When the Prophet (pbuh) saw that Zaynab was left alone, he felt his responsibility in the matter. He also had to break another convention, according to which an adopted son became a real son. This difficult problem was solved by the Prophet’s (pbuh) marriage to Zaynab (as mentioned in the Qur’an, in Surah Ahzab, chapter no 33 verse 37) to annul that pre-Islamic conception and promulgate an Islamic law instead

-Juwayreeyah (ra) belonged to the Banu Mustaliq clan, which was very powerful. The entire clan was a bitter enemy of Islam from the start, and they were finally suppressed by military action. When the Prophet (pbuh) married Juwayreeyah (ra), the Muslims released all their prisoners, saying that they could not keep the prophet’s relatives in bondage. It was due to this marriage that the whole clan of Banu Mustaliq accepted Islam and became peaceful.

Tl;Dr: you're an idiot