Maybe the SRF were at Diana's first wedding and didn't feel like traveling this time around...? The article clears a few things for me as to who these people are:
Diana Bernadotte of Wisborg, born in 1982, is the last of the nine children (born of two marriages) of Lennart Bernadotte, a member of the younger branch of the Royal Family of Bernadotte.
Lennart, who died in 2004, was the first cousin of Gustav Adolf of Sweden, Duke of V?sterbotten, the father of the present King of Sweden, Carl XVI Gustaf. It was the Swedish Crown who donated the castle of Mainau to Lennart Bernadotte.
The civil marriage celebrated Friday is the second for Diana Bernadotte of Wisborg, 34 years. On September 27, 2003, the young woman married Bernd Grawe, 16 years older than her, chimney sweeper responsible for the chimneys at Mainau Castle.
A child was born of this union, February 13, 2004, named Paulina. The couple eventually separated in 2007. Diana Bernadotte from Wisborg is also the mother of a little boy who was born in 2010, Eric Hagen Lennart Bernadotte, and whose father's identity was never revealed - "A private matter" commented her spokesman.
On Friday, the Countess Diana married Stefan Dedek, 27 years old. The young woman, who became a hatter in 2006, met the cook in 2011, during a bowling party. The couple had announced their engagement in March 2015, specifying 22 months in advance that they wanted to marry in January 2017.
Maybe they could have sent CP and Sofia to this wedding? It's not like they have much to do and they might have enjoyed themselves.
P.S. The place looks absolutely amazing! :O Here's the website of Castle Mainau: http://www.mainau.de/de/herzlich-willkommen.html
The PM article is slightly misleading in claiming that the Swedish Crown donated the castle. Wikipedia says Lennart Bernadotte bought it from his father in 1951.