Go tell a Catholic and a Protestant that they’ll the same religion and see what happens.
They tend to have a pretty big history.
And where do you want to draw the line for “same”?
Islam, Judaism, and Christianity all worship the same God.
The one that Abraham heard in his head that told him to kill his brother, then told him to kill his son but at the last second changed their mind.
They have minor disagreements on prophets and what food is allowed, but they’re worshipping the same god a (likely schizophrenic) guy over 2,000 years ago said he could hear in his head.