Did those churches exist already when the Revelation was revealed, cuz?
Yes, of course.
From reading those verses, it is obvious they did.
Excellent observation from you Outstanding!
Can you find any verse that "speaks about how corrupt Christianity will become"?
Until such time that it is finished it is still become.
17 Likewise, every good tree bears good fruit, but a bad tree bears bad fruit. 18 A good tree cannot bear bad fruit, and a bad tree cannot bear good fruit.
