Why is culture important to understand for management?
There are at least two ways in which to read this question. It might refer to corporate culture, or it might refer to culture in the more general sense of the word. Both are important for management to understand.
With regard to corporate culture, it is important for management to understand so that it does not try to do things that are incompatible with the established company culture. If the management does not understand the culture of its employees, it may try to do things that go against the corporate culture. This can throw the workplace into some degree of upheaval as employees struggle with the idea of doing things that are not comfortable for them.
The more general kind of culture is important too. This is particularly true for multi-national companies and for any company with a diverse workforce. Management may not be able to master the nuances of every other culture, but it has to at least be aware of and sensitive to the possibility of cultural differences. Managers need to be able to deal with their employees without unintentionally giving offense or making the employees feel uncomfortable.
In both of these ways, then, culture (whether corporate or general) is an important thing for management to be aware of.