TNA's previous attempt it running a special on a Monday opposite Raw did a terrible rating, in the 0.3 range.  At the time, the number seemed to prove that most of TNA's audience also watched Raw and would watch Raw over TNA.

On 1/4, Raw did above average.  TNA did above its Thursday average.

It seems pretty reasonable to interpret the figures as being the return of a lot of the fans who quit watching wrestling when WCW shut down.

The core WCW audience was still excellent for cable at the end, with Nitro usually drawing a somewhere in the low 2s at the end (the last show drew a 3.0 thanks to the buyout and simulcast).  Raw drew a 4.7 that night (consistent with what it had been drawing normally) and jumped to 5.7 the next week, but it fluctuated throughout the rest of 2001 with no clear influx of WCW fans watching the show.  These fans were gone, and they weren't watching TNA, either.  If they saw Mike Tenay at an airport, they asked him what he'd been doing since WCW closed, a story told by Tenay himself.  Former WWE stars who had relocated to TNA, like Kurt Angle, have told similar stories that ask what they've been doing since they've quit wrestling.

Hogan got some mainstream attention for his move to TNA, but the biggest promotion came from UFC shows on Spike TV.  Maybe all of those lapsed wrestling fans really did embrace UFC.