Like all of us on our first cooks, we sweat it way more than necessary. Seems we're all control freaks at heart! To quote a famous homebrewer's saying - "Relax, have a homebrew!" (meaning, don't sweat it and overthink it, it's not rocket science!)
Mirror the others' comments - a bit more heat soak, as that was a lot of cold protein going on at once. When I use my Guru, I typically keep the fan damper half closed, as the spot where my grill sits has a tendency to be windy, which can impact your airflow more than you think.