"Shrestha" is a broader last name that many Newars can have as a last  name just like Bahun can have "Sharma". So there are people of many newar last names who have decided to stick with Shrestha as last name instead of their "more specific family name". Shrestha can be Chaathare or Panchhare, Chhathare is Chhetris of Newari community.

The rise of  number of people with Shrestha has been drastic since 2007. This is mainly due to two factors. People deciding to stick with Shrestha last name instead elaborating with their specific family name  And 2nd reason, which is more important, is people of many so called lower castes putting shrestha as the last name - due to their inferiority complex or to get rise in social strata.