The MC is written to be quite stupid, isn't he? There are enough hints he got to figure out what's going on, he put a marker on the mustache guy so he should know that he appears everywhere and buys out potions and important ingredients, the old witch has to deliver potions at a set deadline, there are bandits looking for a carriage with an old woman and a girl, then the mustache guy appears at the pub and talks about robbing someone before "the deadline" to use the robbed wares to gain a rank and territory... seriously, the first two points were already enough to figure out what is gonna happen.
