You martingale for a short period of time and few bets try more and Lets see if you'll get the same result as positive profit. But if you do that you must have a big amount of balance to cover your continous losses during martingale. And don't forget martingales work not only for you they works for website as well.
If the site is provably fair, martingale will not work, what happens is just pure coincidence. Martingale is not a loop hole that applies to all dice or online casino site. Its nothing but a glorified strategy that some claims works for them but didn't make them rich at the end of the day because if it is true and working, how come they are still playing and using the so called strategy?