Why wasn't there a tiebraker in the NL Central in 2001?

https://en.wikipedia.org/wiki/2001_St._Louis_Cardinals_season Cardinals and Astros were tied for first but Astros was awarded the title cause they won season series. If that's the case then why didn't the Cubs win division last year since it was the same record and the Cubs won the season series vs Brewers? show more https://en.wikipedia.org/wiki/2001_St._Louis_Cardinals_season

Cardinals and Astros were tied for first but Astros was awarded the title cause they won season series. If that's the case then why didn't the Cubs win division last year since it was the same record and the Cubs won the season series vs Brewers?
Update: @James, it still don't make sense though, since the Cubs beat the Brewers in the season series the Cubs own the tiebreaker, which means Brewers Rockies WC.
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