Where does it state that there is to be a wall of separation? It merely states that the government cannot establish a religion or prevent the free exercise of any religion.
The purpose of the 1st Amendment was not to create the idea or principle of separation of church and state. Instead, the 1st Amendment reinforced the meaning of the separation of church and state principle as it was embodied in the unamended constitution.
In the unamended constitution the government was given no authority in matters of religion: no authority to aid (promote, help, etc) or hinder religion.
As Madison said:
"There is not a shadow of right in the general government to intermeddle with religion. Its least interference with it would be a most flagrant usurpation."
Matters of religion were off limits to the federal government, but the drafters of the Constitution were hard pressed to convince the state ratifying conventions of the built-in constitutional safeguards. Because some felt that clauses such as the Constitution's "elastic clause" might enable a future Congress to circumvent the "no power" over religion directive, Madison drafted and submitted the additional constitutional constraints that eventually became the religious clauses of the our 1st Amendment.
The proper way to understand the religious clauses of the 1st amendment is to realize that they did not create anything, they only strengthened what had already been created and embodied in the unamended constitution.