Does the marriage contract become void if it becomes clear after its completion that the contractor was a polytheist, even though the contract was concluded according to Islamic conditions?

A disbeliever is not permitted to solemnize the marriage contract of a Muslim woman. If this occurs, the contract is invalid.

Deficiency in religion prevents the marriage contract.

As long as the contract is invalid, the marriage is likewise invalid, and a contract solemnized by a non-Muslim is not considered to have fulfilled the conditions of an Islamic contract.