It was Liverpool's first defeat since October, but the points were priceless for Swansea, who cut the gap between themselves and those above the relegation places to just three points.
He said: "I am more frustrated about the performance than the result.
"We were just not good enough, especially in the first half. We didn't play how we wanted to play.
"We didn't keep the right positions we needed to, to cause them problems and didn't stretch them.
"We gave them the opportunity to score and then we did exactly what Swansea wanted.
"They didn't need to play, they needed to fight and we did exactly what they wanted and their confidence grew."
Liverpool missed plenty of opportunities for their normally clinical strikers Sadio Mane, Mo Salah and Roberto Firmino.
They also came up against a goalkeeper at the top of his game in Swansea's Polish number one Lukasz Fabianski.
The only goal came against the run of play in the 41st minute when Mawson swept the ball in at corner and Virgil van Dijk had misplaced a header as he tried to clear.
It summed up an awkward league debut for Van Dijk, who had previously only played in one FA Cup tie since his record 75 million move from Southampton.
- 'He probably has season ticket' -
The frustrations provoked Klopp into his argument with a Swansea supporter around the hour mark and he admitted: "He was shouting at me all the time but I reacted. I am a human being, not just a professional manager.
"I am sure I am not the first manager who has a problem. He probably has a season ticket."
Klopp added: "Swansea knew that to win today they needed our help and unfortunately we gave it to them.
"They did the right things to deserve to win a game like this tonight and we didn't deserve it.
"We could have equalised at the end, but didn't have that luck."
For new Swans manager Carlos Carvalhal, this was a tactical triumph as he used a five-man defence to deny Liverpool space and then hit them on the break.
The Portuguese likes to use seafood metaphors to describe players as either lobsters or sardines, but this time he was borrowing motor racing analogies as he left Liverpool on the hard shoulder.
Carvalhal said: "I talked with my players and said this (Liverpool) is a really strong team.
"They are like a Formula One car. But at 4:00pm in London it will be difficult to speed, they would be a car like any other.
"We needed to make sure there was traffic, we could not let them have open roads to drive in.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)
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