There was no doubt about Kooij's win as he raced well clear of what was an elite sprint group in the end, as Max Kanter finished in second spot while Tim Merlier completed the podium.
The sprint was affected by a crash just outside the final five kilometres, which reduced the peloton and left most of the favourites for the overall classification in a group 14 seconds behind Kooij. '
As such, Tadej Pogacar, Remco Evenepoel, Paul Seixas, Tom Pidcock, Richard Carapaz, Isaac del Toro, Juan Ayuso, Jonas Vingegaard, and yellow jersey Torstein Træen were all caught in that same group, which meant that they suffered some time loss to the front sprinters, but there were no major changes in the overall classification between the main overall contenders.
The 24-year old Dutchman just joined Decathlon CMA CGM earlier this year, and is taking part in the Tour de France for the first time. He was injured or ill for the first half of this season, which meant that he didn't have a chance to race until the end of May and had to go through a tough process to be selected for the Grand Tour stage race.
"After a couple of hard days already, I had to wait to this day to get this first chance to sprint in the Tour, and to immediately win is unbelievable," said Kooij in his post-race interview.
"I think it means quite a lot, just in general, after a pretty tough spring, to get back to this level, to keep believing in yourself, and just a few people who believe in you as well is all you need. To be here with the support of the team today was all I could ask for, and they did a great job."
"I think it was quite an easy day until the final, so you know it will be hectic. In the first sprint of the Tour, everyone is still really eager. I just managed to find my way a bit on my own in the end, but I found the right wheel, and I just wanted to have a chance to sprint today. When I saw the line, I just went as hard as I could."
Tomorrow will be a decisive day in the Tour as the first major test in the Pyrenees features over 4,100 meters of vertical climbing, including the legendary Hors catégorie Col du Tourmalet.