your ebrake probably would have skidded you even worse, its not made to stop the car, it just locks the rear up instantly
great for ebrake slide, but not for stopping. Doint do ebrake slides either though, they're not good. And, it would liekly have sent you into the tree sideways.
Are you on stock tires BTW? I had a similar experience with my stock tires, not so much becasue of traction problems, but because the sidewalls flex a lot, so when you turn and brake, you get a real un stable feeling. be careful