Luke has meditated on the Force in hyperspace before. In fact, he'd received some of his first lessons on relying on the Force in a hold of the Falcon's, hurtling towards Alderaan. Hyerspace and realspace can't normally interact, but that's meaningless to the Force. It's everywhere, in everything, always.

Point is, nothing strange has ever come of it before.

Until now. He'd jerked back to awareness as something shook the entire ship, fallen, and -- woken up on a planet. On a planet, next to a bustling street crowded with ground-based crafts, and just outside the door of a building. If his mind weren't buzzing with shock and the sudden onslaught of millions of minds, he might've noticed that someone's coming through that door -- and he's standing in their way.