The reason why Ojamas sadly don’t work well is that they need too many cards to deal with opponent threats and there aren’t enough resources for all of that.
And it doesn't help that the skill was nerfed. Here, he must have concluded it was hopeless and he was right. I had Canadia and Onslaught waiting for him and a monster was already there so that the board wasn't completely locked up.
They nerfed Land of the Ojamas? Oh, that sucks. I unlocked Manjome in January 2018 and been using that skill since then... guessing they did it before that. Sad thing is that you would come back even if he did manage to lock all your 3 monster zones.