If only nine of the thirteen states were needed to pass the new government, why was it important that all states support the constitution?

It was important in the sense that the states which did not support the constitution were likely to succeed from the union.

It was important for all of the states to support  the Constitution because of national unity. The earlier debates over the Articles of Confederation meant the new nation needed a consensus about its constitutional structure. An affirmative and all inclusive vote signaled consensus and agreement in the new Republic.

b]to spread the message of black power

the answer to this question is the third option. hope this