The article itself gives a negative verdict on this:

  Verdict
  NO
  
  The Döner Kebab was not invented in Berlin.
  
  Popularised here? Ok.
  But there are no participation trophies for that.

And they're correct. After all, you have not experienced döner kebap until you have tasted the original Klingon jIrtaH ghab.

I don't understand how it was popularised there though. It's a staple in France and seems to have no connection to Germany

Doner kebap was invented in Ottoman empire in 19th century. It was also usually eaten inside bread.

Turkish immigrants introduced it in Germany in 70's. However it is true that the current version of Doner kebap in Germany is quite different than Turkish counterparts. (Sauces, toppings etc)

This is plainly false. Doner was being served in both sandwich and wrapped forms in Turkey well before the 70's. It was one of my grandfather's favorite foods growing up in Ankara in the 40's, and I've got family photos with street vendors selling it on the streets of Istanbul in the 60s.

It is true that in Turkey, you'll find the Döner Iskendar (cubes of bread, covered in döner meat, covered in sauce, on a plate) as a very common dish, but to claim that the street food variant was new in the 70's is insane. There are a ton of people alive today who can refute that, trivially.