"I killed the bandits." Saying that, William walked out of the cave, leaving Ronald and his men behind to clean up the mess.
As for the tons of gold coins, valuable things, artifacts, and weapons that were inside that cave, William wasn't interested. These were the wealth that the Wolf had robbed from others.
If possible, he wanted all the stolen things to be returned to the family or friends of the dead ones. Otherwise, the city, Lord Liam, can decide what to do with this wealth. Money was the last thing that he needed.
In his life, he has never been greedy for money. Maybe City Lord Liam will be able to use this wealth to make Emberfall City better.
Also, from the beginning, Liam's request that William send a letter informing the bandits' location before attacking them hints that Liam is interested in their wealth. Otherwise, he wouldn't have said this.