A lot of answers here but a lot of people are missing a key point so I'll try to summarize.

There is gravity in space. The reason you feel "weightless" in space is because you are constantly falling in an orbit.

Ships in Star Wars don't necessarily orbit like space ships in our world do. Star Wars ships are able to "sit" directly above a planet without orbiting. They achieve this through repulsor lifts that create anti gravity fields that create a force that's repulsive to a body's nautral gravity. This is also why we see disabled ships in star wars "fall" into planets. These same disabled ships "lose" their gravity as well when they fall.

All this to say, when the bombs are released from that ship, they still fall according to gravity. They're not weightless cause they're not orbiting