A question about theology,essence, god and creation?

Hence from the question I've asked previously most people agree to the fact that existence precedes essence. On this basis Sarte refutes existence of God and claims God hasn't created man. Because for which the essence should've preceded existence of man's creation. So are we here for no purpose? Is it necessary that man's creation/or for that purpose "universe creation" requires any essence? And if it does how can we prove that? The man is defined in negative terms for Sartre, as opposed to what it is not: thus, an ashtray has been designed for a specific function, predetermined. The essence of the ashtray before its existence. Essence determines purpose and actions. So for man if essence comes after, is there no higher purpose or essence?