Static role creation in MongoDB fails!

I created a user named “user1” inside a “test” db with “userAdmin” role.

I established a connection to “test” db from vault using the connection string "mongodb://{username}:{password}@"

In place of username, I gave “user1” and corresponding password and verified the connection.

Then I tried to create a static role and rotate the “user1”'s password, but when I gave the “user1” name in place of username field, vault is saying "failed to find user1@admin"

My question is why vault is trying to find the “user1” inside “admin” db instead of “test” db? Kindly suggest your ideas.