Why did most of rivers flow north into the Arctic Ocean?

This statement is not accurate. Most major rivers do not flow north into the Arctic Ocean. In fact, only a few relatively small rivers flow directly into the Arctic Ocean, such as the Mackenzie River in Canada and the Pechora River in Russia.

The majority of rivers on Earth flow in other directions, primarily towards larger bodies of water such as oceans and seas. Factors such as the topography of the land, gravity, and precipitation patterns determine the direction of river flow. For example, many major rivers flow south or east in North America, Europe, and Asia, draining into the Atlantic, Pacific, or Indian Oceans.