Maybe one of the brother's is smarter than he seems, but I dont think they planned this themselves at all. It was a lot of planning and studying. Sure, they made the explosives maybe, but I dont know about the rest. I am a fan of the sleeper cell theory and these two did the heavy lifting. JMO.
Can we expand on this theory? Can we sort of back calculate what they planned versus what was spur of the moment so we can figure out how much planning and money would have gone into this?
1. The bombs - there were several, at least 3 larger ones (2 marathon, 1 in the firefight) and some smaller impact ones. But these aren't expensive or difficult to make, sadly. (little $$, little planning)
2. The guns - this might be where there is a trail. How did they get guns and rifles? MA has some pretty good hoops to jump through to register a gun here. Did either of them have a registered weapon? Where did the guns and rifles come from? And the ammo? (some/much $$, some planning)
3. The timing - I think they just picked a place and time where there was guaranteed to be a large crowd, showed up, agreed they'd be a block apart, parted, each planted their own, walked away a safe distance, detonated, then when the first brother heard the first bomb, the second detonates his.
4. Then they went home and #1 must have made more bombs while #2 went to school and tweeted crap and partied. (little $$, no planning)
5. MIT/carjacking - Did they have a plan to do more bombing, and got involved in the firefight first?
6. Suicide charge on police.
I don't know... it doesn't seem very sophisticated. But the guns and rifles they are supposed to have had would come from somewhere/someone.