But again -- it's one week after the bombing, only a few days since they caught the guys. Do you really expect the FBI to have a fully coherent, nicely packaged presentation of all the evidence ready for public consumption? They are still investigating. I'm sure all your questions will be answered at some point.
Sorry but I find it mindboggling that people are worried about these 'mysteries' and jumping to conspiracy theories, just because they don't have the full story immediately available. This isn't CSI, in real life all this stuff takes a lot of time, way more than people think.
On motivation for example, that will only come out after weeks, if not months, of sifting through every aspect of these young men's lives, with a wide variety of experts weighing in.
Motivation is never simple anyway. It's always a mix of the political and the personal. You can't even take the perpetrator's words at face value, none of them are going to say 'I killed people because I'm a loser who sucks at life'.
I think it was a couple years before they figured out how much Timothy McVeigh's motivations were affected by his PTSD.
Life is not always sinister. Sometimes it's just complicated, and messy.