The people who look at benchmarks aren't the ones deciding that way. It's more like "I heard Nvidia makes the fastest GPUs, I'll buy the Nvidia one I can afford."
Sure, but not consciously. People hear that nvidia XX80 is top-of-the-line and then will associate nvidia with higher performance generally.
Do people actually think this way? "I'll buy the nvidia 2060 super rather than the amd 5700 xt (for the same price, and benchmarks higher), because nvidia has the 2080 ti"