If you test Martingale on some simulators, the initial bets of $3-7 with a bankroll of $10,000 and a bet of "always on red" can bring a profit of several hundred dollars. But it seems to me that casino game simulators still differ in real odds from the real game. Casinos have rules that limit the maximum bets. In addition, you can win a good amount of money 30 times and lose it all in one go. This is the Martingale strategy. The main problem is that you can risk a bankroll of $10,000 for a win of a few dollars.
What is going on if you do that experiment is that you have not simulated enough spins of the roulette, so if you were to only simulate a few hundred spins or even a few thousands, there is still a good chance that you could earn money with the martingale strategy, however if you were to simulate one million spins, then regardless of the number of times you ran the simulation, you will always lose, showing that over the long term the martingale strategy always losses.