I answered this question and I will answer it for you. Neither side prevailed. Neither side was the victor. Both sides were equal in wanting something from the other races - human, Minbari, Centauri, etc., whether it was worship, telepathy in the Vorlon´ case or chaos, war, and corruption in the Shadows´ case. And why did they want it? Because they could get it - and they hated each other and wished to fight and kill each other at some point. Both of them. I'll let you think about that one a bit.
The war was impossible to win. It was never meant to happen. But it was the only way Lorien could get them all in one place. War was the only thing everyone had on their minds. Lorien and Sheridan were linked, and through Sheridan, Lorien could guide the process of Vorlon and Shadow acceptance of moving out of the galaxy. And he knew that the other older races would follow Lorien. I do not think it was possible that Sheridan could have figured all of this out without Lorien subtly guiding him along, and maneuvering him into the right place at the right time.
The other part of this answer is about the question What Do You Want? The Shadows were not concerned with the "lesser races" character or who they were. They wanted to know, what did they want, and if the answer coincided with what the Shadows wanted, then they were a good match. Good matches were like Londo, who wanted the Narns annihilated, war, and power for himself. The Shadows wanted war and chaos. They were overt about it. The Vorlons did too, but they were quiet about it and projected a "good" image to everyone. They were just as eager for war and destruction at the end as everyone, destroying planets with Shadow influence and bringing their fleet to meet the Shadows.
