try to spin more than mashing. spinning is easier on the drivertrain, motor, and knees.
I learn to spin more on emtb than on my reg mtb, trying to be somewhat easy on my drivetrain for durability, and more range on battery.
I know some people like to mash, putting a lot of torque using higher gear plus torque from motor, like standing up on steep climb, that put a lot of force on the chain. especially for heavy rider.
and 12 speed chain would not help either, if you keep snapping chain, I suggest go to 10 speed or even 9 speed drivetrain, thicker and stronger chain. I have box component 9 speed 11-46t, easier to adjust than 11 speed, because of wider space between gears, better tolerance for adjustment, also stronger chain overall.