The idea you swallowed in the group project might have been the one that won.

Silence in a group gets explained afterward as politeness, and it is usually closer to calculation: the idea might be bad, people might look at you, letting the loudest plan proceed is safer. So the project runs on the third best idea in the room. Everyone works that out at the presentation, including you.

Say yours in the first ten minutes next time, before the group commits to a direction. One sentence, no long run-up. If it gets passed over you lost nothing, and if it does not, the whole thing goes better because you spoke early.