Theorically, it is possible to make money off a martingale strategy, but not consistently (since we would be still gambling money, and martingale won't change that).
If someone has a big enough bankroll and the casino game they are playing is probably fair, then there is a chance to pocket some money if the gambler recognizes when it is the right  moment to end their session and withdraw all that money.
It happens the same with other gambling "strategies" they won't work because people who try them do not know when to stop and continue to wager believing they could become millionaires in a single gambling session, in the end, they lose all their money.
If martingale was a reliable strategy for anyone to make money off casinos, there would be so many of them going bankrupt each month that passes by.