In order for things to be equal, the strong and the weak must have the same outcome. In order for things to be fair, the one who is stronger should must have the opportunity to become greater than the weak.
The winners don't get it all, they get an amount proportionate to their performance. Keep in mind we're talking about a hypothetical perfect situation, not any actual society you might be arguing against.
fairness don't mean equal chances from beginning, in all cases. For example: It's called fair if disabled persons get prioritized in public places(car parking, restrooms, busses etc.) but this is inequality in between disabled one and not disabled one.
The reason it works like this is because those with disabilities have to work harder to get from point A to point B. Thus their are laws in place to keep those with disabilities from being discriminated against through long distances and the like.
These measures are usually additional infrastructure and measures for giving these people as equal chances as possible, they are not intended to prioritize and/or lower ones over others. Currently, complete equality in the medical field can't always be given, some survive 30 ys, others 90 ys..