Really don't think Klopp would've underestimated them, just think Bielsa would've done his homework and known to attack the space behind our fullbacks and to press us which is what they kept doing.
The lacklustre way Liverpool played the ball about and allowed Leeds to press them into mistakes (VVD gave the ball away for the 2nd goal and the 3rd goal came from a Liverpool throw) would suggest they were too cocky and certainly looked like the players took them too lightly