German company funding a predominantly British based and developed team ( IIRC, the PU’s are Ilmor?) and more than likely, the head nacho’s of the Mercedes wanted a German champion driver.
After all, if it wasn’t for the previous team boss, Ross Brawn, putting in place the development strategy for the PU, then Merc would not have enjoyed their period of superiority. It could all lead to a sour taste in the mouth’s of the paymaster’s and purse string holders.
Hence the garage team swap, unreliability issues experienced and race orders. Job done.
Perhaps NR is aware or has an inkling of this and perhaps this his his way of undermining the fat cats? In which case, fair play to him.
None of this matters in the great scheme of things, regulation changes next year could well prove to end the dominance and give rise to many toys being thrown from the silver pram’s