because in Act 2, Othello was portrayed as a great soldier and he was physically powerful. The fact that he was chosen to give the position to a man with no experience leading men in battle supports this idea.
The period of time that Desdemona lived was not like today; women did not enjoy the same freedoms that they do today. This was a time of strict social hierarchies and rules about women should behave in the home and in public. The rules include they should not speak very often and certainly not about matters of state or important issues, they should obey their husbands and fathers in all things and such. The last rule that I listed is why it is such a shock that Desdemona has had a secret marriage. When she explained about the marriage, it became clear that she is a most admirable young woman. Her speech to her father was wisely presented. She was perfectly respectful to her father and was so clear that her loyalties have moved on. She understood her father and even had some sympathy for her father’s wrath, but she was able to present her wish and finally succeeded to persuade him. I am sure that it would be very uncomfortable for Desdemona herself to be in such a situation, but she did not panic or furiously argued about it. She has ability to communicate with others without leading the conversation to quarrel or fight.