I think that part of it is that as demo trading is consequence-free, it is easy to click the button to enter a trade, and should one have a losing trade or two it is easy to find the steel to get back in and enter new trades, so demo makes it easier to trade mechanically.
Your own example throws up a good example of this: had this been live trading, would you have taken all the same trades had it been a real $100,000 you were trading with? Easy to be brave with monopoly money!
Demo is great for learning one the technicals of how to trade, but does not replicate the psychology of live trading. Most newer traders, when they take a couple of live losses, carry forward some small impact on their next few trades.
So I don’t think that demo trading is rigged as such, but as it does not contain a psychological element, to speak of, it does not replicate everything that is going on when trading for real.
Also, I would strongly recommend demo trading with an amount equal to that which you would have available when switching to live trading. Why pick $100,000 as your demo amount? You can learn all the same lessons with $1500, say, and have it much more representative of your eventual progression into live trading, which must help the learning. It might be exciting to trade demo with such a large sum, but it is just like playing monopoly or something, and is not as relevant a lesson for your transition to live (unless you intend to go live with $100,000, apologies for assuming no lol).
Personally I am not a fan of demo, but if you are then my advice would be at least to ensure that your demo practice is as close as possible to replicating your eventual live trading.
At the moment, it is a bit like learning to drive. You intend to buy a regular car when you pass your test, but are learning to drive on a Pagani Zonda computer game. You might be learning the basic controls, road layout etc, but it is so vastly different from the real thing that it is likely that your performance will take a backward step when you venture out onto the roads for real.
20% return in six weeks is good, but hitting that return live trading at the outset is much harder, imho.
ST