Gas station isn't going to pay unless they get sued basically. Progressive doesn't think the cost of suing them will be worth it. probably an older car and either totaled it for barely anything or rebuilt your engine was a few thousand bucks and having their lawyers try and sue a company like Marathon would cost way way more than that.
They probably also don't have any proof that Marathon is responsible. A random employee at the gas station saying something verbally to your husband is not gonna move any needles