bear in mind that reputation plays a very big role. Zero Lim has been a consistent performer in the world of drifting, hence approaching Toyo should be a lot more easier. Since D1 banned semi slicks, only good tires like the neovas and proxes are allowed. It is a very good opportunity for Toyo Tires to promote their product, and recently...KUMHO is building up their reputation by sponsoring a few more drifters.
Karam is a good rally driver, but can he be a great drifter? That is what makes sponsors doubt his ability. I would love to see him in the autokhana world too as it is much more closer to rally where he specialises in. I've heard of a rumour saying that he was sponsored by Fiat to run the entire season of the R3 time attack, but I don't see it anywhere.
However, if Karam were to join D1, I'm sure that there would be more publicity. Even me myself might start going to the D1 stand to check out how he does.