To me it seemed like Finn was either going to get hit before he made it, or crashing into the weapon wasn’t going to accomplish much. Basically, it seemed like he was making a sacrifice for the sake of it.
I think they made it clear that it was between him destroying the weapon and himself, or saving himself and the weapon. Rose clearly says that basically with the line of “more important to save those who we love, than defeat those who we hate”