Why should Bayern be?
They are the big dog in the most important sports in the biggest economy in Europe.
Their sponsors are usually German or even Bavarian companies that have an international interest. Made in Germany adverstises with made in Germany (and often competes for the advertising contract with other big German companies like in the car market). There is nothing wrong with that. And no - there is no related party. Just 3 companies (independent from each other and owned through shares traded on the stock market) that each own 7% of shares - 75% owned by the club and its fans. The club holds a big majority of the shares and with that the power. The companies just are investors.
Bayern's commercial partners:
https://fcbayern.com/de/club/partner
The big difference might be that in the UK you have several big dogs that have to share the "usual" UK sponsors with each other. The foreign partners in the list (usually minor partners) have an interest in the German market and many you can find at about every big club like e.g. Coca-Cola or Konami/FIFA...