Is it permissible for an employee working in a financial company that provides an e-wallet service, and who has the ability to prevent financial transfers, to transfer customers' money allocated for gambling to his personal account in order to prevent them from the sin of gambling, with the intention of returning it to them later, and is it permissible for him to speculate with that money?

It is not permissible to steal money to prevent it from reaching gambling platforms, because the end does not justify the means, and the means have the rulings of the ends. None of the scholars have ever said that it is permissible to steal gamblers' money to prevent them from committing sins. What is prescribed is to enjoin them to good and forbid them from evil. This also does not justify the intention to return these funds later, especially with no guarantee of one's survival or steadfastness of intention, and given that this action violates the terms of employment and exposes oneself to accusation.