It does work that way, though it's not enough electoral votes removed.

Arizona decertified would bring him down to 295, Georgia would bring him down to 279, Wisconsin would bring him down to 269, Pennsylvania would bring him down to 249, and Michigan would bring him down to 233.

Only three of those states (Arizona, Georgia, and Pennsylvania) would need to be decertified for him to no longer be 'POTUS'. Then again, there are two things to consider.

1. We are in unprecedented times legally so who knows what the conditions need to be. Maybe just one state decertified is enough to remove him from power.
2. The military is probably only waiting on one state to be decertified for all we know.