I think it was chosen because it was the nearest 'big city' to Corvallis. This kid clearly had no resources of his own, the FBI provided him with everything except the desire to lash out and hurt people. I suspect his radicalization had as much to do with fanaticism as teenage despair.

I seriously doubt that there was much of a political decision about directing him to the target. I seem to recall that he chose it himself in fact. If the FBI or the government wanted to make a broad political point they could have loaded him with some fake explosives sent him to an airport to be detected by the back-scatter imagers. That would have scored everybody (FBI, TSA, DHS) some points.

As an exercise in studies on terrorism, I was once part of a group that proposed hypothetical attacks upon American infrastructure, cultural sites, political sites and economic sites.

For a terror attack to be effective you have to have a target, a means to a target and a goal. In the case of this student, he did not have the ability to make a significant strike against a major political-cultural-economic target. So he chose something close and culturally poigniant at the time.

In his case he chose a cultural target to create fear and to assault something that he would see decadent and symbolic of the West.

Personally as part of the exercise, I chose a hypothetical multiple simultanious assault on suburban Primary and junior high schools similar to the Beslan school siege in Russia as potentially one of the most dangerous strikes to the American psyche and economic sectors.