We are basically random. 2% of population by top IQ test result has pretty much very similar distribution in all aspects to 100% of the population. It's not a high bar to be fastest processing one among 50 people.
Given that they are probably rarely in groups of purely random people, if you are Mensa member and you are in a group of dozen people (for example in professional setting) you'd probably have a 50/50 chance of not being the one with the highest IQ there.