It's not even so much about their racing (although that's part of it), it's that reality "showmances" happen all the time, but Rob/Amber were the first and well, so many thought it wasn't real. After Rob proposed on the live Survivor finale, the TWoP recapper (or one of the big gurus there) said that he would eat his hat if they actually got married, because, yeah, really.

But they stayed together, got married and it's been over a year and judging from their interaction on the race, it's real, they're in love. And that also helps, because in all of the races (I've seen them all), there is only one other pair that treated each other with the same amount of love and respect as Rob/Amber.

I don't think they crashed/burned so bad, they screwed up the one task -- which others did as well, and then they just kept falling behind and they had the bad luck of the final task, only 2 for boat, and then had to look through a stack of things, based on luck of finding it quickly.