For a business to build a reputation, it takes a lot of money and time to be invested to achieve this through marketing, brand awareness and all other activities.
Unfortunately these days ready-made scripts and license are available everywhere hence people are setting up business on the go. So, they might be getting ready to run a business within the times of a week. And for reputation, they might be having their own team who will be talking about on every social media and giving positive review at possible places.
Moreover for intentional scammers, only for the first time to build a business might take time and for repeating the same business model for second or third time, they might be coming up very quickly but in different name so that they could scam in quick succession and run away.