Since Muslims believe in all the Prophets equally, why is Muhammad special?
All Prophets were equally from God, and equally true, but the scope of their missions varied. The messengers before Muhammad were each given teachings limited to their respective nations, because in those times a nation did not have much to do with other nations.
Furthermore, the teachings of each Prophet applied for a limited period of time only, after which God would raise another Prophet to revise some of the teachings for the new circumstances.
The time came to unite all the nations upon a single religion so that mankind may live in peace as one nation. Muhammad, to whom God gave teachings for the whole world for all time to come fulfilled this purpose.