Let put it the other way, you don't get 20% chance of each try to success.
You are getting 80% chance of each try to fail.
So instead of 20% x 5 = 100% success in RE. You are facing 80% x 5 = 400% FAIL!!! in RE.
Does it make you feel you were actually very very luck to sucess in only 1 out of 10 attempts now???
That's still not true. In order for 5 tries of 20% to beome 100%, you have to eliminate tried choice.
For example, let's say there are 5 numbers; 1, 2, 3, 4, 5. You have 20% probability of picking 5. If I pick 2 then I'm within the 80% failure bracket. If I put 2 back to the mix, I still have 20% probability of picking 5. If I remove 2, then I have 25% chance of picking 5.
In this case, we are putting the 2 back into the mix. So you will ALWAYS have 20% chance of picking 5. In theory if I pick enough times, I SHOULD have 20% success rate. However, this isn't really guaranteed. Refer to Law of large numbers.