Why did Robby not follow up on the article about the priests?

Question

In Spotlight (2015):

_{Spoilers for the (near) end of the movie:}

Throughout the movie we see that the Globe had received some letters about priests abusing children and that someone didn't think much of it or for some other reason he didn't do much about the story, besides a small article and no folo.
Later we see that it was Robby that had received the letter and didn't do much about it. He said it was a while ago and his memory isn't clear and then Baron tries to cover to him by saying something like 'Sometimes we spent so much time on the dark, when the light comes on, there is a lot of blaming going around'.

But my question is: Why didn't Robby do something when he first received the letter? It was the first clue that could help them.

Answer 1

He simply didn't remember it - and if he had he wouldn't have believed it.

To quote from the man himself, who was interviewed about this:

Question: The movie presents your character as either repressing the knowledge of what was going on or not acting as strongly on the knowledge of what was going on as you could have.

Answer: Yeah. Part of the reason for that being in the movie is that there was a story the Globe actually ran in 1993. The Boston Herald also ran this story, and both papers buried it inside, about this one lawyer, Eric MacLeish [played in the film by Billy Crudup] who basically sent out a press release saying that he had found 20 priests in the archdiocese [who had been accused of misconduct]. Now, in truth, looking back on it and knowing Eric MacLeish, that was Eric MacLeish trying to get attention to himself so he could get more clients, which he did. We published this story and we buried it.

When we started our investigation eight years later, that clip didn’t surface. None of us remembered it. Back in 1993 I think I had been metro editor for about a month when that story ran. I had no memory of it, although I actually think I was on a golf vacation.

So the possible reasons he gave are above:

1. Truly having no memory of the event.
2. Even if he had memory of the event, doubting its authenticity.

I think the film shows that he is not guilty of suppressing information, but that everyone has been guilty of simply missing information.

As the screenplay states at the end of the film:

ROBBY We buried the story in Metro. No folo. Sacha found the clip.

BEN That was you. You were Metro.

ROBBY Yeah, that was me. I’d just taken over. I don’t remember it at all. But yeah.

The room quiets. Gut punch. Ben shakes his head.

MARTY Uh, can I say something?

They turn to him.

MARTY (CONT’D) Sometimes it’s easy to forget that we spend most of our time stumbling around in the dark. Suddenly a light gets turned on, and there’s fair share of blame to go around.
(then)
I can’t speak to what happened before I arrived but all of you have done some very good reporting here, reporting that I believe is going to have an immediate and considerable impact on our readers.
(then)
For me, this kind of story is why we do this.

So many people missed so many signs and they were all somewhat culpable. As Marty says though, they were stumbling in the dark and now they've found the light - and all they can do is report it as best they can.