The Champions League win was the only real impressive part, the rest is actually pretty comparable to Ten Hag at United.
Ten Hag's overall win rate at United is currently 59.8% and he's also reached 3 domestic cup finals in two seasons.
The football was always pretty uninspiring with Tuchel at Chelsea and the wheels started coming off badly for him towards the end. Hindsight has looked very kindly on him with what's happened since at Chelsea but I still think they were justified in sacking him.
The combination of Boehly being viewed as incompetent, Tuchel being sacked pretty early after his takeover and a lot of stock being placed into Chelsea's Champions League win have all led to quite a lot of revisionism. I also doubt he would've been able to get Chelsea to qualify for the Champions League through the league again in 22/23, so the part about qualifying every season is slightly contentious.
They had won 3 of their last 9 games in the 21/22 season and only 3 of their first 7 in 22/23. It was a sustained run of poor form that probably wouldn't have improved much even if Tuchel was given the opportunity to stay on longer. Meanwhile, he had fallen out with their £100m signing and the goals were drying up.
Not with context.
Tuchel inherited a mess from Lamaprd over midway through the season and managed to reach The FA Cup final while beating teams like Real and City during their CL run (winners), and also finished 4th. Those 4 months alone are better than anything ten Hag has done at United.
Now let's compare their 2nd seasons.
Tuchel was given Lukaku and Sául (loan with an option to buy) after winning The CL and securing top 4. They finished 3rd (74 points) during his only full season and lost just 8 games in all competitions. ten Hag lost 12 games alone during his debut season, and that's with multiple signings and a full pre-season. This is ten Hag's 2nd season and he has lost 17 games. Tuchel only lost 16 games across his
entire 100 game reign. ten Hag lost almost double that (28 defeats) from his first 100 games. He's now on 29 defeats from 107 games. His win percentage is actually 57.94% currently.
Tuchel had to manage 63 games during his only full season due to them playing in multiple competitions (6 due to The UEFA Super Cup and Club World Cup). They scored 122 goals and conceded 51 goals. United played in 62 games last season due to deep cup runs. United conceded 43 goals alone in The PL (38 games) compared to 51 for Tuchel over the entire 63 game season. Chelsea only conceded 33 goals in The PL that season. They also outscored ten Hag's United comfortably. 73 PL goals compared to 58 PL goals for United last season.
Let's compare their record vs the top teams during their reigns:
Tuchel:
City - 3 wins and 2 losses
Liverpool - 1 win and 4 draws
United - 3 draws
Spurs - 5 wins and 1 draw
Arsenal - 1 win and 2 losses
Leicester - 3 wins, 1 draw and 1 loss
West Ham - 3 wins and 1 loss
Overall = 16W, 9D, 6L
+14 GD
Ten Hag:
City - 1 win and 4 losses
Liverpool - 2 wins, 2 draws and 1 loss
Chelsea - 2 wins, 1 draw and 1 loss
Spurs - 1 win, 2 draws and 1 loss
Arsenal - 1 win and 2 losses
Newcastle - 1 win, 1 draw and 3 losses
Villa - 4 wins and 1 loss
Overall = 12W, 7D, 12L,
-14 GD
Tuchel took 10 points from 18 before he was sacked. ten Hag took 12 points from 18 during his opening 6 games last season. If ten Hag could achieve 3rd from 12 points from 21 points initially, it's not impossible for Tuchel to secure CL football again. I doubt your doubts based on 6 PL games. Abramovich leaving was the worst thing that ever happened to Chelsea. Tuchel would have been given time to work with the new players they signed that summer. And they wouldn't have let some of the players go that they did.