The answer is quite simple, really.

1. They never questioned it and didn't have the resources to research it in their day.

Simply put; they didn't have the internet.

Every last one of them were taught that Marcionian Gnostic dualism. That Judaism and Christianity are separate.

I've already proved that Rome changed the Sabbath day and that it was not changed in Scripture.

Many others know it as well.

But, I can't force anyone to change their practices. Only God can show you the truth.

I will always defend the traditional 7th Day Sabbath.

May the Lord Jesus Christ bless and preserve you.