This is a very, very, simplified version of why Mullahs sanction things that are forbidden in Islam.
Who are the Mullahs?
There is no ordained clergy in Sunni Islam, by which is meant that anyone can study Islam. Since we are far removed from the days of the prophet (saw). the correct interpretation would involve learning the language (as understood in those times), history and context of revelation of specific verses, and the practice of the prophet and his companions.
There is no ordained clergy in Islam. But in effect it exists among the shia, and used to be among those sunnis who follow the fiqh of one of the (four) Mujtahideen. Also among the sufis there is an oath to obey their sufi leader.
What happened was that since the distances were great, people came to rely on those locally resident who studied the sharia. Many communities were greatly isolated, and gradually their practices became ivergent from the mainstream, or extraneous elements entered their practice, and became sanctified because some religious figure had been seen doing them.
People forgot that they could lead the prayers; they even forgot the meanings of the verses, so they appointed someone who would lead them in prayers. They forgot Arabic, so they appointed Qaris to teach reading the Quran to their children.
They forgot the rulings of basic duties, so they came to rely more and more on those who had more knowledge than themselves, however deficient these themselves were.
In wanting to be saved, they accepted mystics as leaders. These mystics, or sufis, had denied themselves many pleasures, and had acquired some supernatural powers. These sufis then became the virtual rulers of these communities.
After the fall of Baghdad, the religious scholars came to the conclusion that this disaster had befallen the Ummah because of internal strife among the Muslims, caused by free interpretation, so the conditions for scholars to make Ijtihad were tightened.
Thus a door that was considered leading to more divisions of fiqh, was closed.
At one time the Mullahs were learned, and could undrstand and argue intelligently. The state of knowledge of Mullahs isn't always very high these days. In villages the Mullah or sufi pir (leader) is often in league with the local landlord or local political leader, so often the practice is not Islamic, but a tradition of that community.
When a village council, or village Mullah issues a verdict, we discount it, but the community in which they are living does take their word to be true.
Please remember this difference. The verdicts that are issued by the Mullas are not always those of true schoalrs of Islam.
It is a problem of educating our people, and freeing them from the local landlords and local pirs.