For me, it is ridiculous (somewhat) to see a user with member rank becomes a moderator. I don't offend lower rank users but the rank and the total received merits (that in turn affects their current ranks) are some of good things to glance at their contributions. As being mentioned above by the others, another type of contributions and maybe the most important when admin looks at your application is your report history.

Conbitrutions, reports, trusted, and good understandings on forum rules. Lack one of them or all of them, then there is no probability to become staffs.

AFAIK, the staff who began at low rank is Halab (one of the most recently hired staff, since 2018 maybe), from Full Member rank if I am correct.