Conversely Merc need to think about 2-3 years down the line, who 'takes over' when Hamilton retires, Bottas isn't that driver. Having Russell in the team for 2 years, gives both the best indication of whether he could (compared against 'the best') and also gets him settled in, and I really don't think Merc mind who wins as long as one of their drivers does, and they've made it clear they will use team orders when it makes sense.
I'm never sure I believe that, nobody remembers who won the WCC in any given year, but they remember the driver *and the team they drove with*...
Merc's earnings come from winning WCC not WDC... Follow the money