The definition of terrorism doesn’t say you need to terrify people at all.

Besides, there’s been a lot of acts that are generally agreed to be terrorist acts, that have targeted a very small group of people, such as a religious group, or even one specific individual. The IRA’s famous reply to Margaret Thatcher comes to mind.

It seems his goal was to terrify one small group of people, namely senior people in the healthcare industry, and I think that counts.