Bielsa's men had won their last seven Sky Bet Championship games, and most recently staged astonishing comebacks against Aston Villa and Blackburn.
But Leeds looked jaded against a belligerent Hull side, for whom Jarrod Bowen scored twice, and could find no way through.
Bielsa said: "Until now, the team has given a positive response.
"We ran enough and we dominated the game. When you don't dominate a game, you make less effort.
"The performance of the team was not particularly different from the other games we played.
"Usually we have three times more chances to score than the opponents and we dominate games - this game was no different in that sense.
"Maybe we should have had more long-distance shots, but our play on the sides (wings) was similar to what we usually do.
"But in the offensive play there was less precision than usual."
Leeds had their moments, but Hull goalkeeper David Marshall was not excessively troubled throughout the game.
By contrast, the visitors looked especially potent on the counterattack, with Bowen and Kamil Grosicki in excellent form.
Bowen opened the scoring after 25 minutes when he cashed in on poor Leeds defending.
The talented winger then doubled Hull's lead after 58 minutes when he coolly followed up a rebound after more good work from Grosicki.
Leeds remain top of the table, and Bielsa predicts a response when they travel to Nottingham Forest on New Year's Day.
He said: "Our expectancy is to have a positive result next Tuesday.
"The opponents scored two goals and they could have scored a third one, but I don't think we played bad, defensively.
"We had eight or nine chances to score, but that was not a high number when you take into account the possession we had."
Hull head coach Nigel Adkins was in jubilant mood as his side claimed a fourth league win on the bounce.
They are now in 14th place, having earlier in the season looked like prime relegation candidates.
Adkins said: "The lads were great. It was a memorable victory.
"We defended well because we needed to - this is a tough place to come.
"Our shape was good. Grosicki and Bowen were a massive threat.
"Our two centre-back were also immense, but the whole team contributed."
Adkins added: "I'm really pleased for our travelling fans and that we were able to keep the crowd quiet in the first half.
"The objective before the season was to stabilise the football club.
"There's still a lot of work to do, but everyone is working hard - as a team."