So when our statistic 3d play one 1d player he got 82% chance of winning
If he take another 1d player he still got 82% chance of winning
We got states:
our 3d could lose both games, win one or win both of them:
chance of 3d losing two games = 18% * 18% = 0.18 * 0.18 = 3%
chance of 3d losing one game of two = 18% * 82% = 16%
chance of 3d winning both games = 67%
If you take those six 1d players we got 0.82^6 chance of winning ALL SIX games = 30%
This is approximate simulation, because to get more accurate results we should use probably Bernoulli scheme, but the difference is clear
But we are still considering 3d who is merely a 3d (that means he is in lower part of win/lose ratio required to advance from 2d to 3d). If we consider "strong" 3d the chances are considerably higher.
So if you consider even an army of 8k-2k it would be VERY hard to overtake a 3dan player (statistically)