He divorced his wife to prove to his family that he's not scared of her while not wanting to do so
First:
It is important for you to realize that divorce is a law from the laws of Allah and a limit from His limits that he has made clear for His slaves and warned them of crossing it or marginalizing it.
Allah, the Exalted said while clarifying divorce and its rulings (what means): “Divorce is twice. Then, either keep [her] in an acceptable manner or release [her] with good treatment. And it is not lawful for you to take anything of what you have given them unless both fear that they will not be able to keep [within] the limits of Allah. But if you fear that they will not keep [within] the limits of Allah, then there is no blame upon either of them concerning that by which she ransoms herself. These are the limits of Allah, so do not transgress them. And whoever transgresses the limits of Allah – it is those who are the wrongdoers. And if he has divorced her [for the third time], then she is not lawful to him afterward until [after] she marries a husband other than him. And if the latter husband divorces her [or dies], there is no blame upon the woman and her former husband for returning to each other if they think that they can keep [within] the limits of Allah. These are the limits of Allah, which He makes clear to a people who know.” [2:29-230]
At the beginning of soorah at-Talaq, Allah, the Exalted says (what means): “O Prophet, when you [Muslims] divorce women, divorce them for [the commencement of] their waiting period and keep count of the waiting period, and fear Allah, your Lord. Do not turn them out of their [husbands'] houses, nor should they [themselves] leave [during that period] unless they are committing a clear immorality. And those are the limits [set by] Allah. And whoever transgresses the limits of Allah has certainly wronged himself. You know not; perhaps Allah will bring about after that a [different] matter.” [65:1]
So Allah, the Exalted clarifies that opposing the laws which He prescribed for His slaves is turning away from what Allah has permitted and is an oppression of themselves by doing it.
The Prophet (may the Peace and Blessings of Allah be upon him) warned of the transgression of the transgressors and the jest of the jesters concerning His limits; An-Nasai reported from Mahmood ibn Labeed (may Allah be pleased with him) that he said: The Messenger of Allah (may the Peace and Blessings of Allah be upon him) was informed of a man who divorced his wife three divorces all together. So he stood up angrily and said: “Does he play with the book of Allah and I am amongst you!” Then a man stood up and said: Oh Messenger of Allah, shall I not kill him?! In Buloogh al Maram, al-Hafidh ibn Hajar said: Its narrators are reliable.
Abu Musa al Ash’ari (may Allah be pleased with him) said: The Messenger of Allah (may the Peace and Blessings of Allah be upon him) said: “What is the matter with people who play with the limits of Allah: I divorce you, I take you back, I divorce you, I take you back.” Reported by al-Bayhaqi in as-Sunan al-Kubra, declared sound by al Albani.
Second:
If you explicitly pronounced the words of divorce and said: you are divorced or a divorcee, or I have divorced you, or my wife is divorced, or so and so is divorced or a divorcee, or I have divorced her, then a single divorce has taken effect and you may take your wife back as long as she is in the waiting period (‘iddah).
That is because for the explicit divorce the intention is not a condition, rather the divorce of one who does so jokingly takes effect just as the divorce of one who is serious.
Ibn Qudamah (may Allah have mercy on him) said: “If he comes with an explicit divorce, it is incumbent upon him whether he intended it or not.” End quote, al-Mughni (8: 280). See also question number 44038.
Third:
It is upon you to resolve the problems between your wife and your family with wisdom and to give each of them their rights. Your mother and sister erred when they remained silent and did not warn you against pronouncing divorce, and we hope that they now realize the danger of their actions and instigation.
It is not a shameful thing for a man to love his wife and strive to please her, as long as he continues to fulfill the rights of others.
We advise you to find separate housing for your wife where she can live away from your family and it can be near to where your family resides so you can combine between fulfilling their rights and living with your wife fairly.
We ask Allah to assist you and grant you success.