A Weird Situation
I got just the right shield cracking troops on my side to do such a task.
"Don't hold anything back," I released all the fallen gods I had, "destroy this shield at once!"
During all this time, I didn't use any of my fallen gods or any big warriors at all. I kept them hidden for the same situation I was dealing with right now.
The only possible answer for the enemies to not use shields before now was that they never thought I'd have the ability to crash their portals at all!
And so, they acted in response to my sudden ability and found the right way to counter it.
If I used all of my big cards from the beginning, then things would end up quite bad for me. The enemy would have enough time to think and consider how to counter each weapon I got, ending up with me having nothing to crush them or make a change to the entire situation just like now.