It is certainly puzzling and has thrown up many theories of some sort of orchestrated attack. I thought it was a random attack initially. Then came multiple arrests so immediately you start thinking it must be planned especially with it happening on her own doorstep.
They have released those first two though and it's really about how significant the "pending further investigation" part is. It could well be the first arrest was the "date", no extension was asked for, so was it just a matter of questioning and confirming he was where he said he was. The second arrest could also have been able to provide an innocent explanation for whatever reason police arrested him, again there was no extension. Could be in the vicinity or even close to the man they have now arrested in some way. Maybe he loaned him his car or was seen with the wanted man moments leading up to the attack but had nothing to actually do with it, this could apply to both arrests of course.
I'm not sure if they had actually had something to do with the crime that they would be released. They surely would represent a flight risk given it's such a heinous crime. It's all down to the wording I suppose and perhaps someone on here with experience of police procedure could provide some insight.
JMO But I think this man was unknown and acting alone. Another sexual predator. But there are so many oddities, like the carrying her over his should for such a distance, possible coke can used as a weapon! Really is impossible to know what to make of it all.