It was the placement of the bombs that made them less deadly. The triggers and hardware worked reliably, and did show expertise. I'm pretty sure the investigation will turn up that a pro either trained them or handed them the triggers ready made.
I'd think pro training would have incorporated the vehicle bomb, which is not some kind of technological breakthrough, having been used for a century including during the Wall Street bombing. Does anyone really think bombing a marathon made for bigger headlines than an Oklahoma City-style bombing would have? McVeigh attempted to minimize non-government casualties. If he had chosen a street with buildings on all sides, a thousand people might have died. A Islamist pro isn't going to be worried about these niceties.
Amateur terror cells, incited by generalized rhetoric from jihadist websites, in poor communication with any central structure.
That's what we have in our country right now after over a decade of taking it to AQ overseas, but doing nothing about it here.
So what's your point?