Their recent surge can mostly be attributed to other factors besides simply Rondo's absence, as it would be asinine to think this team is better without him. Their bench has greatly improved as well as their ball movement. Paul Pierce and Kevin Garnett have been playing out of their minds, likely at levels that are unsustainable.
Most of all, a recent easy schedule is the main reason for the seven-game winning streak. They have been fortunate to play some easy teams as well as some struggling teams.