There's no big mystery to this.
Use soft slicks, full downforce, and maybe put your gear ratio up a bit, so that bob hits the limiter a bit later than the opponents. This way he can always pass at the end of long straights.
Pit at the middle of the race, no need to let the tires wear down more than that. The opponents really struggle near the end of the race because their tires are shot. Then they pit in the second to last lap, or something. Your bob will outpace them almost 10 seconds per lap at this point, if you already have a new set of tires.
I raced this one as soon as it became available, and my bob won all the races with atleast 40 seconds.
I did an accidental extra pit stop at monaco, and my bob spun a few times in the chicane the AI tends to spin at, at Nurburgring. Still, he won both of those races, too, with huge marginals. I started Suzuka with the wrong tires, so bob had to pit at lap one, and fell 40 seconds behind, he still ended up lapping everyone.
So yeah, the FGT series was one of my bob's most dominating performances.