It's maybe oddly phrased, but in much of Europe, the state did assume power over marriage from the church at some point. Sometimes very dramatically, such as during the French Revolution, when priests were banned from marrying people in the traditional manner and people were compelled to register their marriages with the government. I can see why one might describe that as stealing marriage from the church; or if not stealing, then perhaps expropriation.

Until 100 years ago there was no civil marriage in my country and no civil laws regarding marriage, it was just some penal law punishing polygamy. Then the state took ownership of the notion of marriage by regulating it by law and forbidding churches to perform marriage ceremonies unless you get married by the state, so the religious marriage is just a ceremony with no legal implications these days.

So yes, the state stole the term. It's like tomorrow the state decides by law that everything that color red will be called color blue, that would be stealing the word "blue" and use it to define the color of red things. It is not a natural evolution of language.

> So yes, the state stole the term

But if you keep going back, you get to a time before the church controlled marriages in Europe.

Generally, marriage is a cultural thing, and it tends to be religious at any point in time to the extent the culture is religious at that time.

Yes, there was a time then marriage exist before religion, but it was not regulated by the state. The evolution would be unregulated->church->state. I think the unregulated and church ones are very close in term of legal implications (almost none), while the state is severely intervening and basically destroyed it in recent years.