Making an alt in Salem takes more interaction, but a lot less time. I still don't see it as a problem, though, because it takes a lot more resources to make an alt that can do any crime, so losing those alts will hurt quite a bit.
Anyway, I think the reason for Haven's alt explosion is the same as the reason for hunger bots. Both issues are caused by making consumption of resources the character development bottleneck rather than the production. This IMO is a completely flawed design that has to change. It's virtually trivial to max out one character's mentory with decent curios, and since there's no equivalent of hunger bot for curios, the only thing one can do with excess curios is making an alt factory.
There's two possible solutions that I see - either removing the mentory size limit, or making decent curios harder to get. I favour the latter, and I think the best way to do it would be to add crafted curios that combine base curios into a single item. These should give less total LP than their constituent parts, but they'd pack more LP into less slots. So a more casual player would just use the base curios while nolifers would grind combo curios all day. We need some middle ground between bronze steeds and pearls anyhow. IMO all of these should combine things from different industries (foraging included) to further reward good village organization and generally make a tighter economy. Hell, they could even make worthless stuff like cat gold actually valuable.