They knocked out 2018/2019 Barca with several of their key players injured. A bit like Spurs knocked out City mainly due to Son. Anyway that was a strong Liverpool squad but not at the level of Messi, Xavi and Iniesta etc. It's klopp who elevated their performance. Of course shite teams don't dominate the CL, but the worlds best managers can win the CL without having world class players in nearly every position.
Or : Any manager who enters the competition with a team can make a deep run or win the whole thing. Like Klaus Topmöller, Roberto Di Matteo, Pochettino and so on even without WC squads. All those managers got their teams to a CL final with teams punching way above their weightclass (Leverkusen, Chelsea (won the thing) and Spurs) and they all got fired within 8 months later.....Deep runs in the CL doesn't necessarily mean you are a WC manager.
Players decide matches, not managers.
Liverpool knocked out Barca on the back of a single great performance and a lot of luck, and if Ousmane Dembele wasn't such a horrible finisher that tie would be over before the 2nd leg....
Klopp is a great manager, a fantastic manager, don't get me wrong, but he like any other top manager needs quality players of the right profile to produce results over time, and some luck to go with it. If you give Klopp all the credit for that 4-0 win against Barca, you need to give him all the credit for the crap season they had last season as well, and the 0-3 defeat they suffered 2 weeks before the 4-0 win. A quality squad is of course the main key to good results.
Spurs got past City after Lloris saved a penalty and Laport singlehandedly gave away 2 goals in the 2nd leg, the Ajax tie was even more lucky....It wasn't like Poch masterclassed Spurs to that final, that was pure chance going Spurs way.
Of course players matter more than managers:
Barca: 2008 - 2018. That squad was bound to win stuff with any top 50 manager in Europe.
Won 5 Laligas, 5 Copa del Reys, 1 CL and 5 other trophies post Pep with 5 different managers.
Real Madrid: 2008 - 2018 That squad was bound to win stuff with any top 50 manager in Europe.
Won trophies with 5 different managers since 2008.
PSG post Qatar: Bound to dominate domesticly and will eventually win in Europe with their squads with any top 50 manager in Europe.
Won Ligue 1 and domestic cups with every manager they've had since Qatar took over, except Poch (who will walk the league this season).
City post Abu Dhabi: Bound to dominate domesticly and will eventually win in Europe with their squads with any top 50 manager in Europe.
Won the PL and domestic cups with all 3 of their managers post Abu Dhabi.
Bayern: Bound the dominate domesticly and win stuff in Europe every now and then with any top 50 manager in Europe.
Have won the Bundesliga with 11 different managers since 1996. Klinsman, the only permanent manager since 1996 who wasn't able to win the BL with Bayern was fired during his first season.