Because countdowns, er, count down at the start of the turn of whomever they belong to, and the AI’s Mischief CDs were generated on your turn. You only get one chance to remove them if the enemy has 4 or 5 covers on green, unless you use OBW’s blue, Snarky Remark, etc.
Actually, I had just that happen yesterday in the Simulator node with Bagman, Quicksilver and Modern Mags. Magneto fired off a Magnetic Flux and Bagman snarked around. Since there was only one timer, he increased his own team’s.
Well done, you!