It’s useful to think of a timeline and pin the action or actions on the different places.
Is the action in the past but finishsed? Is the action in the past but its effects linger till now?
Is one action in the past before another one, also in the past?
Is a sudden action taking place at the same time as one continuous action?
If you see it visually, it will all become clear.
Past Simple - actions that started in the past, ended in the past, and have no direct consequence for the present, which is being discussed.
Present Perfect - Actions that started in the past, ended in the past, but have a consequence on the present. (“I have stopped smoking.” = I stopped in the past, and since I am still not smoking, the past action has a consequence on my present)
Past perfect. An action that has happened in the early past, ended in the early past and had a consequence on another action which happened in the later past.
“By the time Susan found out (later past), she had already bought it for him (earlier past)”
We don’t know the context. It might have been:
Last year, when your wife was kidnapped, although it was me who had paid the ransom, you made such a fuss afterwards and told everybody it was you.
(two past actions, one before the other)
Anyway, there’s still a mistake by the corrector. They should have said “it was me who…”, just like you said. Tenses are very difficult to handle. Your images are really good. Actually, you could make a post about that, right? It would be very helpful for everyone!
That was an imaginary example, invented by me to illustrate the concept of the two past actions one before the other. I have no idea of the real context of the subtitle that was corrected, and since I don’t know, I reserve judgement.
I don’t think I need to make another post with the same subject. This one is very suitingly titled “Correct tense”, so I suppose interested people will click on it.
By the way, here are some more. The first one in my opinion is the best so far.