Grail-kun was getting sleepy. Maybe it was the choice to switch from popcorn to more adult beverages. Could a Grail be in its cups?
The diminished party of Servants was also running low on mana. Even with the threat of more evil amongst them, enthusiasm was dragging.
"How about the lilac-haired chick?" someone asked. "She's just kind of planted herself there, not making us think she's particularly good."
The Servants coalesced into a loose circle around Mash. They egged each other on to all focus their destructive power on her. "...I just wanted to help the Master. Notice me, Senpai!" she wailed.
The Master did indeed notice Mash, as she retreated in shame, her face purple with embarrassment. Everyone held their (mostly non-existent) breath, waiting to see how the miasma of evil might change with her elimination.
Nothing. Grail-kun yawned and vomited a bit. "How about you all spend some time getting a different perspective on this situation, look at it in your spiritual forms. Come back and see what you think later."
One by one, the remaining Servants disappeared, until all that remained was Grail-kun, a flustered Master, and a large shield, rocking slightly in a phantom breeze.