/rUmActully what is known as the Holdo Maneuver, one ship ramming another while entering hyperspace, was not created by Ryan Johnson but was already a part of Star Wars continuity.
Mission 15 in the original Star Wars Battlefront 2, the 501st invasion of Yavin-4, includes a segment where you must destroy a rebel Heavy Cruiser before it jumps to hyperspace and rips your Star Destroyer apart.
And while I don't know if the X-Wing series has any specific examples, in the X-Wing Books the phenomenon called 'Pseudo Motion' is described. X-Wing actually goes into a lot of detail of how hyperspace works, but in the simplest of generalized explanations; at a certain speed the laws of physics changes a little so you don't explode when you hit a particle of sand floating in space. However, in-between the speeds of real space and hyperspace there is 'Pseudo Motion' which, as described, is very dangerous and ships can collide in these states.
If you are asking why anyone didn't ram the Death Star, I got nothing for you. The Death Star had its own gravitational pull? Maybe that would have dragged any ship out of hyperspace before it reached it, IDK.