It's got a long history and really began in earnest under the W Bush administration. A lot of govt money started flowing toward religious schools and organizations around this time under the guise of traditional religious culture being a bulwark against terrorism and a source of right-thinking soldiers for the war.

The law only applies when it's actually enforced by the judiciary. And the Christian theocrats have been infiltrating school boards and government bodies for decades to try to violate the separation to privilege their denomination above all others. Usually advocacy groups like the ACLU or satanic temple will try to contest the change in law or use it to show they can't violate the establishment clause without violating the first amendment of the US Constitution.

They're using this to provoke challenges against the wall of separation between church and state. They feel confident, with good reason, that the christofascist majority on the Supreme Court will reinterpret our Constitution to eliminate that law.