The Reds maintained their one-point advantage at the top of the Premier League as braces from Sadio Mane and Virgil van Dijk, together with Divock Origi's first league goal since December, secured an emphatic victory.
Manchester City remain hot on their heels, however, following a 1-0 win over West Ham at the Etihad Stadium.
Mane's brilliant backheeled second will likely be seen as the game's defining moment but both of his goals were laid on by Alexander-Arnold, who also supplied the delivery for Van Dijk's first.
"All the crosses were outstanding. So it's just a special night," Klopp told the BBC's Match of the Day.
"He scored a fantastic free-kick the last time against Watford. I can't remember the last time he got a hat-trick of assists. He got three right?
"We want to use our power and our skills but there are different games to play. Watford changed for us too. You always prepare for a match differently. We used that half space well. Mo Salah was pretty much unplayable."
Liverpool had drawn three of their previous four league games, but never looked like dropping points on Wednesday.
"It is just a really good night for us and the boys deserve all the credit," added Klopp.
"The boys showed how much they enjoy the game and the situation. It was an important sign. You know what was written and said about us. It is of course not right. These boys are outstanding and they showed so much passion.
"The game from Mo [Salah] was incredible. Sadio [Mane] scored a brilliant goal. All three midfielders were outstanding. Both centre-halves played outstanding.
"We won 5-0 so you don't talk about them but they had their moments. Even Alisson was great. The boys who came on controlled the game. A lot to talk about."