The sea level rose. Yes, because the Ice melted. Had to go somewhere, ha ha.
But, I am talking about the earth’s crust.
Think of it as a foam mattress. It IS springy, and it sprung up a lot.
There are two basic types of surface rebounding. One, as you pointed out, is a spring back of the land after the enormous weight of the glaciers is gone through melting.
The other involves bedrock that was driven deep into the crust as the result of the mountain-building process (tectonic plate convergence). The rebounding in this case occurs when the great weight of the overlying mountains is no more due to them having eroded away.
For example, the surface bedrock seen in Manhattan’s Central Park, and other areas along the east coast, was once several miles below the surface. It appears at the surface today only because the overlying mountains eroded away, allowing the land to gradually spring back up. They are what’s known as (former) mountain ‘roots’. The mountains there are believed to have been once as high as the Alps. And the land (the entire North American continent, actually) was SOUTH of the equator.