before austin he wasn't putting up big numbers
wm13 was a huge dud
What do you mean "Before Austin"? Austin was just as big of a part of Mania 13 and those programs in 1997 as Taker was, and just as similarly Taker was a big part of the WWE programs when the company got hot.
Hot concepts and angles drive ratings and business. The WWE didnt start getting hot until Tyson got involved, McMahon turned and became the perfect heel antagonist, and they went all in on "attitude". It was similar to how the WWE didnt really take off in the 80s with Hogan until they got Lauper/Mr. T involved, and they developed "Rock n Wrestling".
Besides, when taker was champ he was going up against the white hot NWO angle, and creatively the company had been a wasteland for years so they had to win back fans slowly. Taker was always a fundamental piece during good times and bad.
Additionally, in 1997, the WWE was experiencing a lot of backstage turmoil with the real life Hart/HBK feud, which was negatively affecting the product. Ideally, Taker would have never been put in that position to headline had HBK not "lost his smile", and submarined mania to get out of doing a main event job.