Earlier quoted context omitted.
Every rule has an exception, and maybe Larry has perfected something there or has a very well managed ego. Most Co-head situations I see are either higher-ups setting up a power struggle between 2 newly appointed co-heads, or an existing head pretending to step back by appointing someone as their co-head who they can sabotage in real-time.
I wonder if the dynamic is simply ownership. Larry is still the largest single stockholder of Oracle (~27%). So everyone knows he still runs the company at the end of the day. Benioff only owns ~2% of Salesforce. There's institutional investors who own more of Salesforce than even Marc.
Their first non-German leader (Anshu Jain, who didn't speak German) was made Co-CEO with an older German hand Jürgen Fitschen from the board.
They pushed out Jain after 3 years, brought in a Brit John Cryan (who spoke German!) to co-CEO with Fitschen. Fitschen stayed on another year after which they finally let the non-German, Cryan run the place as sole CEO for 2 years before replacing him with another German as sole CEO.
So in total there were 4 years of non-German co-CEOing with a German, 2 years of a non-German actually being sole CEO, and then back to a German again like the rest of their 153 year history.