Hi,
There isn't a setting that you can toggle this behavior on and off with, and most assets will try to "smartly" align themselves with the ground they're being dragged in on.
There is an easy solution for this, though. Underneath the Scene Graph in the right of the window, you should see an expandable panel that is set to Statistics by default. If you select this and change the panel to display the Transform panel, you can then easily adjust rotation of the model by setting the Y value to 0, orienting the model horizontally along the world axis.
I hope that helps!
Best,
Raghib