I saw a Youtube video that posited that Holdo calculated to hit the ships at the moment before the ship entered hyperspace, when the ship was travelling at relativistic speeds, and applies physics to it to explain why it makes sense (and yet sort of doesn’t).
Nerdist: The Physics Behind The Last Jedi’s Coolest Scene! (Because Science w/ Kyle Hill)
With regard to how it doesn’t makes sense, he says that if the math works out, her ship hitting the fleet at relativistic speeds should have atomized the entire fleet rather than merely breaking the ships in half.
I guess that the scene established that the GFFA doesn’t obey this specific law of physics, and at the same time it does. I mean, it obeys it, but the result is only a fraction of what the actual result IRL would be. I guess that also means that the power of the impact any Rebel cruiser could create on the Death Star wouldn’t be enough to destroy it?
Anyway, I remember leaving the theater and overhearing a considerable amount of people (even the people who I went to watch it with) asking “why didn’t she simply lightspeed herself into the FO before? Or why have they never done that before? It’s so useful and overpowered…” So even if I don’t have a problem with that I totally understand why some people would.
The way I understand hyperspace working is that it’s a dimension weakly coupled to normal space, so that ships traveling through hyperspace would still need to ‘avoid’ masses but a crash would primarily affect the object in hyperspace. Under this theory, any ship going to Hyperspace would damage that ship far more than the target.
But what if the hyperspace tracking technology used by the Supremacy means that the ship is always partially in Hyperspace? After all, some part of the ship would need to interact with this dimension at all times for it to work. Under this theory, the First Order is undone by its own technology and hubris rather than an overpowered exploit of the ill-defined rules of the universe.