The corruption has come via the master of it - Satan, his throne is the Vatican.
The corruption it would appear, started somewhere around the 100's, and bit before maybe, and well and truly grew by the 3 - 400's and sealed in concrete, so to speak.
They are responsible for the said 30,000 other followers, being off the key core and necessary truths, hence it would appear the Advocate is of little effect, other wise it should be impossible to have 30,000 odd.
2 Thes 2:11 is certainly in play, ppms only true God in 17:3 being Father, Son and Holy Spirit, despite Jesus defining the Father independent of himself, is clear proof of this.
That is astounding.
Not to mention he also says, when the word God is used, it always means Father, Son and Holy Spirit.
Which means the likes of -> I ascend to my God -> Father, Son and Holy Spirit =
Due to the 2 Thes, people have no idea as to the numerous stupidities that the trinity makes out of numerous verses = astounding as to the power of this 2 Thes and it will continue until Jesus comes and exposes the lies in their Temples and then comes the wrath, it would seem.
The Great Tribulation is the least of their worries.