The market now measures performance regardless of ownership. Just because they retain a huge percentage of shares, or controlling interest, doesn't mean they'll accept massive declines in market value.
It means they can though. The tech world is full of examples of companies keeping their focus long-term due to dual class structure and/or founders retaining large stakes despite the vagaries of the market.
But, nothing lasts forever. Eventually the founders sell, the shares get converted to common, etc.
But, nothing lasts forever. Eventually the founders sell, the shares get converted to common, etc.