NBC is trying to capitalize on anything that gives it big ratings, and the only thing that can do that now is The Voice. 
The network is trying to squeeze as much Voice out as possible to make way for another ratings winner, summer reality entry America’s Got Talent.To do this, NBC is expanding The Voice to two nights starting April 2nd at 9p.m., as The Biggest Loser will shrink to one hour. The Tuesday Voice episodes will air for six weeks and will serve one-hour result shows to compliment the 2-hour live performance shows on Mondays.
Once The Voice wraps up its season May 8th, America’s Got Talent will return to NBC earlier than usual, May 14th and 15th with two-hour episodes.
This is a strategic move on NBC’s part. NBC will get a much better rating on Tuesday adding The Voice to the night; and with moving the premiere of America’s Got Talent up to the final weeks of the official TV season, AGT will air directly against the final two weeks of Dancing with the Stars, in hopes that AGT will put a dent in ABC’s vulnerable reality franchise. NBC is trying to capitalize on any vulnerable franchise possible to build up their rating share at the end of the season.
America’s Got Talent settles into its regular Mondays at 8, and Tuesdays at 9 timeslots starting May 21st.
TV Talk With JWalk 