That 1 player is still against the mafia
Assume ratio of 15-4-1
It takes 3 days of perfect conversions (which again I'm betting on limitations on number and who can be converted if there is a cult) to reach the size of the mafia. At the same time mafia can hit town and if town is lynched, after 3 days its 9-8 town vs scum (assuming just 1 hit and no vig, cult, or extra mafia hit
If there is a known cult outed then it makes more sense....but we know nothing right now