Why would anybody bomb a sports event....just a bunch of peeps having drinks, and watching the race....no policy makers, just regular people. It makes no sense to me...but random violence is beyond my comprehension. I pray for everyone affected by this horrible act.
Soft target, it's that simple. Something like this is easier than an army base of government building.
Regarding people at events not being involved in overseas military activities. That isn't the way the terrorist sees it. To them, by not rioting in the streets and doing everything you can to keep removing leaders, until you get one who will stop all the military activities, you are by default approving the activities in question, whether you actually do approve or not.
Not saying that's my view, but that's the mindset in question.