They've got a strong squad that never should have been in that position. More a sense of turning the dressing room attitude and team spirit around rather than purely tactical.
The irony of someone else mentioning Moyes, he's actually made West Ham more defensive, taking over from Bilic's more attacking play, and they've been much more successful - no one really mentioning that though.
I agree he has made them more defensive, but he does not shackle his potential match winners into defending before attacking.