Lots of speculation. While we know the older brother, at least, is religious, and muslim, we don't know that THAT is the cause of this. They have lived here for ten years. So, if all of a sudden they decided to go sectarian and blow stuff up for the cause, the operative question has to be, when, and where, and who convinced them of this?
The worst thing you can do is draw a conclusion, at this point. Any number of possibilities are still on the table.
It seems to me, that with the number of explosives these guys have been tossing, and apparently grenades as well, that they have been preparing for this for a while...months, maybe even a year or two. This was not a, "Hey, I got a couple bad grades, let's go blow up the Boston Marathon!". This was a planned attack. But why? I doubt they are sleeper cells that have been in the country for a decade. Just seems unlikely. The FBI is probably going to do a pretty in depth study of the last couple of years on these fellas, and hopefully, spill some of those beans for the rest of us. Till then...no one knows ****.
