Is the restaurant owner considered sinful if men and women frequent it mixed, knowing that this is the business he excels at?

If the restaurant is one where men and women intermingle, and it predominantly has a Western character, then it will contain abominations such as women displaying their adornment, reckless intermingling leading to immorality, and illicit relationships. The intermingling of men and women is the root of every tribulation and evil; it leads to an increase in immoralities and fornication, and it is among the causes of widespread death. Allah has forbidden assisting a disobedient person in his disobedience. Whoever sees an abomination should change it. Therefore, it is impermissible to open such a restaurant in this manner due to its assistance in deviation and abomination, and it is advised to abandon this work.