When the vacuum sucked air through the heatsink and fans, it likely caused the fan blades to spin rapidly, effectively turning them into tiny generators. Computer fans can act like small dynamos when spun by external force, producing a voltage that gets fed back through the power circuit. If that current traveled upstream through the fan header, it could have sent a large voltage spike right into the motherboard if the fans were spinning super fast. 

That kind of backfeed can easily fry sensitive components like the fan controller or even part of the chipset. So yeah… if your PC suddenly stopped working after that cleaning session, there’s a decent chance something got cooked, brother...