I get what you're saying but soap is like really hard to make without being able to buy the ingredients like lye and so on
Almost all ancient novel i read that centered within merchant or business genre ..soap is the easiest to make ..some of the transmigrator even purposely sell the recipe to a rich business owner and get one lump sum money because how easy it was to copy the soap after buying few times, for poor mc .. it's kinda risky to make and ro sell independently.. simplest soap can be done with lard , wild flower/herbs and wood ash ..but if the mc is dirt poor , using lard for soap might get a beating from his family
He made toothbrushes at first. But he couldn't think of making soap? If he made people think that hygiene is absolutely necessary then he could've made more profits. Then he could've made more female customers with beauty products. Seeing him operate a club is also weird. He made high rise building with an elevator that works with manpower. But a type of paternoster elevator be more efficient? Well, even that elevator needs a motor, so I guess there's no other way. But seriously though, he's not using his modern knowledge properly. I feel like he could've done more.