What is the ruling on three employees, who receive their salaries from the state, closing the mosque and going to a social event, which caused confusion among the worshippers?

As long as the employees receive salaries for their work in the mosque (leading prayers, calling to prayer, guarding), they must fulfill their trust so that their salary is permissible. It is not permissible for them to neglect their work or be absent except for a legitimate excuse, such as illness. They should be advised, and if that does not work, the matter should be referred to their employer.