(disclaimer: I understand a lot of what is written here is generalizations but it's just what I've picked up on during international travel)

How much luggage are you normally carrying? My experience has been if you are carrying more than one medium sized luggage (and a notebook bag/backpack), chances are your CBP search chances will go up. Also, when you're being asked questions when getting your passport checked, avoiding eye contact and speaking in a barely audible voice screams, "I want to be searched."

Also if you told the CBP you were attending a concert, what kind of concert? Normally if you are seeing friends at the concert, I personally would've said I was visiting friends. That is not a lie. What I'm saying is your saying you were at a concert could possibly be misconstrued.

In the past, I've always wanted to beat the lines/crowds etc. but in doing so and being in a rush also attracts attention. I find it hard to believe that your being brown skinned and Asian is an automatic red flag.

It's really hard to answer your questions such as why is the CBP singling me out? I hope that you do find some sort of resolution to this situation.