You cannot fake a number
Similarweb is the first tool a partner, an investor or a competitor opens to size up your website. Its traffic estimate becomes your reputation, so a weak ranking costs you deals before a call is booked.
To improve Similarweb ranking, then, you cannot fake a number: you have to raise the actual website traffic the model reads, on a curve that looks like real growth. That is the whole job: more genuine website traffic, better engagement, stronger visibility.