Kämna countered a Kenny Elissonde (Team INEOS) attack on the final rise to the finish line in Megève, powering clear of Davide de la Cruz (UAE Team Emirates) and Elissonde to take a breakthrough WorldTour win after a tough, mountainous day in the saddle.
"I'm so happy with this victory, my first ever professional win and to celebrate it here at the Dauphiné is such a big thing for me," said Kämna. "I'm so glad about it!"
The win was tinged with sadness for Kämna and the team as the squad's general classification contender, Emanuel Buchmann, crashed on a dangerous descent and withdrew from the race with severe contusions to the abdomen. Teammate Gregor Muhlberger also withdrew from the race with a fractured wrist from the same fall, along with Steven Kruijswijk (Jumbo-Visma).
Race leader Primož Roglič was also caught up in the crash, but remounted and despite clear abrasions and missing bits of his jersey, the yellow jersey wearer seemed none the worse for wear in terms of performance, retaining the top.
"Today's strategy was actually for me to be a relay station for Emu, the plan was for him to attack in the penultimate climb, but unfortunately, he crashed, so I went for it," said Kämna. "It's a bittersweet day... I hope all the best for Gregor and Emu and that he's back in form for the Tour de France.
"I'll enjoy this moment now, give my best tomorrow again and then look ahead at the rest of the season, most probably the German Championships and the Tour de France."
The day was a dramatic one from a general classification perspective even before the crash on the descent from the Col de Plan Bois. 2019 Tour de France winner, Egan Bernal, withdrew prior to the race with the team saying that he had been suffering from lower back pain.
The crash that caught up the general classification candidates was criticised by Tom Dumoulin (Jumbo-Visma) who described the poor quality of the road and its dangerous nature as the reasons for the crash.
"It was a disgrace that that descent was in a race," Dumoulin said of the road coming down from the Col de Plan Bois. "The whole descent was really tricky but the first two or three kilometres were full of gravel, pot-holes, bumps in the road, 15 per cent drops down.
"That they still put things like this in a race is… well, I'm really angry about it and I'm pretty sorry for Stevie that he has to go home because of this because he was in great shape."
The battle for the stage was up ahead with the breakaway, but back in the peloton, the race erupted on the major climb of the day, the Montee de Bisanne. Bahrain-Mclaren went to the front of the main bunch with 43 kilometres remaining and slimmed the peloton down to just an elite group, with contenders including Richie Porte (Trek-Segafredo) and Romain Bardet (AG2R La Mondiale) losing touch.
Roglič, however, was never in obvious difficulty and teammate Dumoulin was all over any attacks that attempted to move clear of the group containing the favourites. Despite the chaos caused by the Bahrain-Mclaren aggression, the Jumbo-Visma presence neutralised the race, and the majority of the dropped climbers returned to the fold on the descent from the climb.
The general classification battle cooled down from there and there wasn't any attempt made on the final climb to the airstrip in Megève to attack the lead of Roglič, with a hard day in the mountains still remaining in the fifth and final stage of the Criterium du Dauphine.