If you read the Bobitza, Lisa and Danny example, just imagine Danny's fishing net broke again at the end and he had to buy a new one ... 10 times in a row. At the end, all money will belong to the bank as profits from interest payments. Next time Danny makes a loan, Bobitza will have no money to buy the fish thus Danny will have to default.
My example was only offered as a way to explain how it works with your extremely unlikely and really impossible scenario that that one person owns all the units of currency and is loaning all of them out at once to a single person. You'll notice that in the example I gave, Lisa has no need for currency for a period of 11 weeks. In the real word this is very unlikely.
To start with, in a world with only 3 people there really isn't a need for a currency. Assuming there are more than 3 people in the world, the Bank will need to use those profits to continue to exist. They will need to spend them on operating expenses. Bobitza will need to purchase more than fish. At a minimum he will need to cover the operating expenses of his fishing supply business. He will have other people making purchases from his business, so he may not need to use funds from his bank account to pay for Danny's fish.
Your problem seems to be that you are looking at currency as a static thing. Bobitza loans Danny 10 units, then Danny hands back 110 units all at once before any time has passed. Money gets reused over and over as time progresses. My example was trying to who you how it was the exact same 10 units of currency that kept moving in a circle between Bobitza, Danny, and Lisa to pay off the 110 units. Once the loan (and purchase) was made, there was no need for there to be 100 units in existence any longer.
You are right that if a single person significantly out produces everyone else providing something of significant value to everyone, then they can and will amass a very large some of currency over time. The effect is amplified in an example where there are only 3 people and 10% of the entire economy is being moved around on a single transaction. Yes, if Danny has to repeatedly borrow from Lisa, and Lisa has no need to ever spend the currency (or spends significantly less then she earns in interest), then she will eventually own all the currency. On the other hand, if Danny sells 10 currency units of fish to Lisa once and continues to supply fish to Bobitza for 9 more weeks, then Danny owns all the currency. Of course, if Lisa and Danny both buy fishing equipment from Bobitza and he withdraws all his money from the bank, then Bobitza owns all the currency.
In reality, all these "ifs" balance out along with the millions of other people using the currency. The money continues to flow throughout the system, and interest continues to be paid.
Here is an analogy that might be poor, but it works for me.
Assume a bowl of water with exactly 15 units of water in it. You have a spoon (or ladle) removing 1 unit of water from the edge of the bowl. You scoop this water from as close to your right hand side of the bowl as possible. Then you pour it out into the same bowl as close to your left hand side as possible. How many times will you be able to perform this action before all the water piles up on the left hand side? The problem you have is that the water continues to move over time filling in the area where you scooped it from other nearby areas and moving outward from where you dumped it to other nearby areas. So the right hand side of the bowl can continue to pay the left hand side indefinitely as much interest as needed.
Now the economy can be manipulated and individuals can suffer from that manipulation. If all the areas near the right hand side of the bowl decided that they weren't going to give that side of the bowl any more water (essentially building a wall to prevent water flowing into that area), then eventually the right hand side would run out. If the left hand side were to start hoarding and refuse to allow water to flow out (building another wall on the left hand side) then the left hand side would end up with more than most areas that are still participating in the economy. But unless the left hand side is willing to spend some of that water into the economy of the bowl, it isn't going to be very useful to them. An area in a bowl of water doesn't need to participate in the economy of the bowl to survive, but we humans generally need to participate in the economy around us for survival.
The way that Bitcoin deals with the situation of removing currency from the economy is to naturally end up using a smaller amount if bitcoin for the same type of transaction (delfation). In the water bowl example, all of the participants end up using spoons that shrink over time getting smaller and smaller, so that they are moving ever smaller amounts of water in any given transaction. This deals with both lost wallets (water spilled out of the bowl), and hoarding.