Credit Karma factors the age of your collection as part of your Average Age of Accounts.
Its one of the reasons Vantagescore is a joke. Your score dropped because the removed collection dropped your AAoA probably under a year.
Your FICO score would have likely rose, especially if it was your last derog.
How CK does it: (the wrong way)
Collection - 4 years old
Good Card - six months old
AAoA - 2 years 3 months
How FICO does it (the right way)
Collection - 4 years old
Good Card - six months old
AAoA - six months
The fact that CK (as well as nerdwallet and other vantagescore freesites) considers collections as open active accounts is really stupid, and if they just fixed that, it would eliminate a lot of the issues of VS3.0
In fact a few months ago one of my collections changed to closed status and the same thing happened to me, my scores tanked 40 points on CK (unaffected on FICO since FICO wasnt calculating them wrong from go.
