The Pole, who won the rainbow jersey in 2014, joined Team Sky - now Ineos-Grenadiers - in 2016 and became one of the men riding themselves to the ground in the mountains to help Chris Froome (38), Geraint Thomas (37) and Egan Bernal (26) claim the Tour title.
Kwiatkowski, although he won the Milan-Sanremo Monument classic in 2017, put his personal ambitions to one side and his bent, broken figure on a zig-zagging bike midway through the Tour climbs has become a common sight in July when the team turns into a grand tour machine.
On Friday, though, Kwiatkowski looked more like his old self, a classy rider able to hold off a chasing pack and attack from the breakaway to take his second Tour de France stage win after 2020, when he beat Ineos-Grenadiers teammate Richard Carapaz (30).
That year, then defending champion Bernal pulled out of the race injured on the Col du Grand Colombier and Ineos-Grenadiers did not win the Tour.
"Winning on top on a mountain where I have memories of Egan Bernal quitting the race is special," said Kwiatkowski.
"With Richard it was a different feeling because that day we could enjoy the last 15km while today was one of the hardest efforts in my life."
Kwiatkowski started the final climb (17.4km at 7.1%) with a four-minute lead over the bunch but in the final kilometres, where he fended off a sea of flag-waving fans, he had no idea how close the chasing groups were.
"I didn't have the team cars behind me so I didn't know what my lead was. It would not have been possible without the fans, they were driving me to the finish, it was an amazing feeling," the Pole said.
"I had 18 friends in the breakaway. At first I thought it was just a free ticket to the bottom of the climb but I never thought we would be fighting for the win because (Tadej Pogacar's) UAE Emirates (team) were pulling so hard on the flat. It's crazy."
What would have happened if Kwiatkowski had chosen another path and focused on individual success?
"I don't live in the past, it's not the way to do it. I always look ahead and try to think positively about what is coming. I don't think about what I've achieved or not achieved," he said.
"It's unhealthy to think about the past all the time. Yesterday was a very hard day for me and today I'm at the top of the podium."