Lucky just turned 15 today, it wouldn't be off the mark to say people got a chance to look up Britney's earlier videos as well.
Britney also just released a single recently. Even though Pretty Girls flopped it's gotten a good amount of views (it's almost Vevo-certified). You know damn well Gags has been off the grid for some time now.
EDIT: like everyone else said, it's also a much bigger hit.