Mercedes needs to do a complete 180 to become an electric car manufacturer. Employees with education and years of experience in internal combustion engines will fight their obsolescence. Plants and production lines that are specialized for ICE manufacturing will buck against the change. Their supply chain, dealerships, and repair shops will have the same problems and will also provide resistance.
It's one thing to pivot a little start-up company that's maybe a few dozen people who have just been applying generic engineering and sales techniques to a domain that they've only just invented in the past year or two. A behemoth like Mercedes does not pivot. It trundles along and slowly, almost imperceptibly, shifts course over a long period of time.
Mercedes needs a lot more horsepower for the battle than Tesla does.