confuse between math and physic (for displacement)

if displacement is the shortest distance between two point then that would also meant that it is equivalent to the hypotenuse when using phytogaras theorem right?. but why isnt displacement the shortest length between two point ?because Xinitial - Xfinal couldnt posibly be the displacement (shortest distance between two point is from phytogaras theorem. where Xi^2 + Xf^2=displacement^2) this is soo confusing. please help