Like several other manufacturers over the years (Honda, BMW, Ford to name three) they'd have been better off just being an engine supplier in F1. They could have linked up with an established team, offered sponsorship, engines and technical support, and cleaned up with their resources.
So now they're leaving. Ford sold the Jaguar team to Red Bull. Honda cut and ran. BMW have dumped what remains of the Sauber team on some investors with a dubious background and buggered off. Well done guys, was it worth all that cash? Mind, at least in the case of Ford and Honda they've left behind teams that have gone on to do well. I can't see what's left of Sauber doing well if they make the grid next year, and I can't see the Toyota team doing well if they get bought out and make the grid either.