CBS welcomed back The Big Bang Theory (2.3 rating in the adults 18-49 demographic, 13.3 million viewers) after two weeks off and saw it dominate the primetime landscape Thursday, taking the tops spots in the demo and viewership and, teaming with Young Sheldon, the night’s No. 2 ranked how in both metrics, gave the network an overall win on the night. That said, Big Bang had looked like it was building momentum toward its finale (scoring a demo 2.3 on January 17, 2.4 on…