So, this is just theory and speculation, so please take it as such. I am bored as I wait for day 2 to start.
1) Houston Texans wanted to choose Will Anderson at 1.2
2) However, front office was split, ownership wanted a QB, face of the franchise who could put butts in seats and sell tickets, whether it be Young or Stroud. And coaches buy off that either can also win games in our system.
3) This leads to the comment that these QBs are 1A/1B, meaning either could fill that role, depending on who was available and ownership would buy in.
4) Texans explore trade ideas to land Anderson at 1.2 and 1A/1B at 12, or trade up slightly.
5) Then rumors about Stroud begin to leak and hurting his draft potential (but helping Texans chance of landing him a few picks after our first)
6) Panthers lean heavy towards Young, Texans front office quickly learns that pick 1.2 is the lynch pin that the rest of the draft is eyeing. Meaning if we don't pick a QB with our first pick, a bidding war would take place at 1.3.
7) It is decided that Strouds draft value wasn't hurt enough to justify the gamble on waiting for him to drop. Nor could they allow the bidding war for 1.3 to begin by passing on QB.
8) Stroud is chosen at 1.2, effectively minimizing those trade offers to Arizona for 1.3, allowing Houston to trade back up for their initial favorite draft choice, Will Anderson.
9) And the crowd goes wild!!
Long story short, the trade up wasn't so we could choose Will Anderson. The trade up, was so we could choose a combination of Anderson and Stroud without having to miss out and settle on one or the other.