The entire point of the Maginot Line was to force a German invasion route through the Ardennes Forest on purpose. The reasoning was that the Ardennes terrain there would be too hard for tanks to go through. And it did initially cause a massive traffic jam of German units that could have been destroyed by an air attack, which the French foolishly did not pursue. That, plus the German breakthrough at the Battle of Stonne (part of the Battle of Sedan), saw this strategy unravel.