In a providential universe , virtue is the sole good because providence is guiding things. So we trust things will work out for the best.
But without providence we have decide what we value , which is a challenging task. It's funny to see modern stoics stumble on this point. They can never explain why virtue is good , because they destroyed the foundation for that belief. That's why they aren't able to become a sage, there is still doubt hidden in the subconscious mind.
This is where epicurus saves the day with long term pleasure as the sole good.