Namely, even though they were all, broadly speaking, Christians

The majority of the founders were deists.

https://www.britannica.com/topic/The-Founding-Fathers-Deism-and-Christianity-1272214

Although orthodox Christians participated at every stage of the new republic, Deism influenced a majority of the Founders. The movement opposed barriers to moral improvement and to social justice. It stood for rational inquiry, for skepticism about dogma and mystery, and for religious toleration. Many of its adherents advocated universal education, freedom of the press, and separation of church and state. If the nation owes much to the Judeo-Christian tradition, it is also indebted to Deism, a movement of reason and equality that influenced the Founding Fathers to embrace liberal political ideals remarkable for their time.

it was only a matter of time before someone whose religion was not agreeable to take over and start doing things that you don’t like

Not just a disagreeable religion, but any religion.

https://firstamendment.mtsu.edu/article/establishment-clause-separation-of-church-and-state/

Both Jefferson and fellow Virginian James Madison felt that state support for a particular religion or for any religion was improper. They argued that compelling citizens to support through taxation a faith they did not follow violated their natural right to religious liberty. The two were aided in their fight for disestablishment by the Baptists, Presbyterians, Quakers, and other “dissenting” faiths of Anglican Virginia.

The christo-fascist MAGA movement is not consistent with the origins of our nation and the Constitution despite originalists claims to the contrary. We are not a christian nation, but a secular nation. All religions, including Christianity, were deemed dangerous to mix with the government.

I'm sure you didn't mean anything by it in your argument, but these misconceptions are what the MAGA movement will use to push christian nationalism on all of us and to exclude people based on their faith or lack of faith.