All the acts of the Prophet Muhammad (SAWA) and all the prophets are according to the will of Allah (SWT), still we find some wives of the prophets disobeyed Allah and been mentioned in Quran as examples for the nonbelievers like wife of Nuh and wife of Hud.(Sura 66, Verse 10).( Allah set forth an example of those who disbelieve, wife of Nuh and wife of Hud, both were under two of our pious servants, but they betrayed them......).
The marriage of Zaynab Bint Jahsh is mentioned in Quran very clearly being ordered by Allah ( ZAWWAJNAKAHA) ( We made her your wife)( Sura 33, Verse 37).
Not all the wives of the Prophet are on the same degree of Imaan , as we have in the history that Qateelah Bint Al-Ash’ath was one of the wives of the Prophet Muhammad (SAWA) but she left Islam after the demise of the Prophet and got married to ’Ikrimah Bin Abi Jahl.
Many marriages of the Prophet were for securing and protecting Islam from harm like his marriage with Um Habeebah, who was a daughter of Abu Sufyan, the head of Disvelievers of Makkah, and sister of Mu’awiyah.
Marriage with A’isha was suggested by Abu Bakr, her father, to the Prophet and was accepted by the Prophet ( SAWA) to avoid Islam any harm, and also to provide the Ummah a test which distinguishes right from wrong after the Prophet.