Jave

I'm experiencing what feels like vibrating from the rear on my 99 4runner when braking. I don't really feel it in the brake pedal but more like in the seat and it seems to be coming from the rear of the car.

I'm pretty sure this started after I was adjusting the rear drums.
They were too loose so I tightened them but did it too much so the rear brakes were dragging. I drove like this for maybe 40 kms before I adjusted them to stop dragging (stupid, I know.)

Could this have caused the problems I'm experiencing now or is it likely something else and just a strange coincidence (I'd be very surprised if that was the case.) If it was from driving with the brakes dragging, what has likely happened exactly?