From the council of Nicea in 325 until the present the concept of the Trinity has always been the Father, Son, and Holy Spirit. Mary was never viewed as God and an omnipotent god would know this to be true.
You said that ,and you got the proof there are many who beelived Mary pbuh is divine and still millions of people believe that.
Do you still claim Quran made a mistake ?
Yes. What a minor sect believed is not the issue.
Why ? One and only G-d warns also a minor sect if they make a mistake.
The sect may be minor but it is the biggest sin to associate a partner with G-d.
And there is much bigger discuccions in the christian world about the subject.
THE TRADITION OF MARY,
THE GREAT GODDESS
BY BROTHER MARKUS
From the second century there are several reports about a movement, named collyridians by its opponents. The members of this movement worshipped Mother Mary as goddess. The name collyridians was given to them, because of their practice of offering cakes. A practice that is already reported in Jeremiah for the jewish worshippers of the Queen of Heaven. Although tracks are lost of this movement, the second name that had been conferred on that people "philomarianites" (lovers of Mary) has been used again and again over the centuries by catholic church officials, for those worshipping Mary as goddess. Unfortunately they condemned such tendencies and looked upon them as errors of mislead individuals or sects.
http://www.womanthouartgod.com/traditionofmary.php
I believe secrets of Fatima concerns her only.
The basics of the teachings of the all prophets are not secrets and they are very clear , secrets do not have a big role in the G-d's teaching.
Openness of the message is the basic point in all revelations.
One and only G-d does not hold responsible anyone for any secret but He holds responsible for open warnings and messages they have received.
Peace