Easy way to get huge gain on demo account over a long period of time, for example 16 times the starting fund:
Step 1: Open 16 demo accounts with starting fund of $1000
Step 2: open a huge position (for example 10 lots) for those accounts, Long for 8 accounts and Short for 8 accounts.
Step 3: When 8 accounts opposite to the market have blown up, close the winning 8 accounts immediately.
Step 4: Now you have 8 accounts with 2x the fund = $2000 each
Now repeat 4 steps, but this time with 4 long 4 short, you will have 4 accounts with $4000 each
Repeat that again you will have 2 accounts with $8000 each
remember when you are operating this scheme, take some time gap between each cycle so on the timeframe it looks more trustable.
At the end you will have ONE account with $16000, which is 16 times the original fund, congratulations.
Declaim: OP I am not saying you did your demo account like that, I am just explaining why people wouldn't trust a demo account result because of those schemes exist.