[@Days]
I think in Thierry's mind he felt that marrying Nick put Nick on a way different level to Theo and hoped Theo would realize that Nick was a romantic interest and not a replacement of him. Backfires of course and instead alienates Sabrina even further. I think the only person it legit helped was Nick and maybe helps Thierry realize he's too involved with his work later down the road. I do think Thierry is in love with the idea of being in love and has a strong desire to take care of somebody... he's just not taking care of the right people. In this regard, Nick really does represent his midlife crisis.

You bring the popcorn, I'll bring the pizza rolls! And several boxes of tissues...