Attendance and ratings didn't "collapse" immediately following the turn it wasn't until the Fall during the Invasion flop when there was a true decline in ratings and business.
Attendance in 2001: https://sites.google.com/site/chrish...s/avghouseshow
Not on the level of 1998-2000 but still stronger than it would be in 2002 after the roster split, the Fall portion of the year were huge down months for the time though.
Ratings in 2001: http://www.gerweck.net/tv-ratings/2001-ratings/
Smackdown's ratings dropped a bit but Raw's were constant throughout the year although there were some months where they were noticeably lower than others.