The most advanced cossack troop got panicked after deployment. By one of the special effects of Fire and Sword.
Next squadron lost its melee with the reiters, fled and ran into already disordered cossacks, making them flee also and leaving the dragoons badly stranded on other side of bridge, alone.
Well they were non-noble anyway so no big loss.
The pancerni watched the whole episode with disgust. When Swedes brought infantry and artillery to the bridge colonel Opalinski decided to let Swedes have the lousy bridge over meaningless brook and deploy his host elsewhere.
The special effect was a fair turnaround since we've had the same thing happen the other way round.