I think because it wasn't known whether there would be 2 teams as rivals (porsche as well) even though they're both owned by VW, or they would compete under one

I think because it wasn't known whether there would be 2 teams as rivals (porsche as well) even though they're both owned by VW, or they would compete under one name. I think othe other option was that they would only supply engines, if I remember correctly. Anyway, it's great too see them joining!