One thing that might have played into that is that in large group situations, if you're just a grunt, a cog in the wheel taking statements, one of many, you might inadvertently inject your own perception of the sense of importance of a witness or statement, and pass that up the chain. Humans are fallible. So say Mr. CO has RA on his list of people to follow up on, takes a statement, and gets it into his head that RA is either (a) a harmless goofball that doesn't fit the profile, or (b) is a lonely confused guy that's trying to inject himself into the investigation for some exaggerated sense of self-importance. Or (c), maybe at the time of that interview, LE already had a very strong feeling it was somebody else, and this lesser character didn't bubble up enough to overcome that tunnel vision. And then, as has been said many times, that info is lost among the thousands of other tips for whatever reason. I've been involved in large-scale events where the fact-gathering is farmed out to a large number of people, and it's really easy for something to get glossed over in those situations.
I really hope that whatever happened that caused that first interview to be ignored or forgotten is scrutinized really closely at trial, because I feel like there's a real opportunity for a teaching moment here, a potential for improved processes. I'm pretty hesitant to throw dirt on LE this early in the game, at least until we know who specifically screwed up and how. LE is not a monolith, it's a bustling collective of people fighting competing priorities.