To be fair, the economy was still fairly strong by that point. It wasn’t until 06-07 that the subprime lending really got out of hand, and even though 07 was technically when the recession started, it didn’t become a full-blown panic until 2008 when Lehman Brothers and Bear Sterns collapsed.
The yield curve is like seeing upturned leaves in the wind: a storm may coming, but it’s not clear when.