Any amount of civilian ships has zero chance of breaking through even a small Navy’s determined effort to stop them. The purpose of these ships is to put Israel in a bind. Hurting foreign civilians that are on a peaceful mission would be bad politically. Letting them through would make Israel’s blockade look like a joke and probably encourage others to do the same. Even stopping them without hurting anyone is showing the world that Israel doesn’t want civilian aid going into Gaza. They likely know they will be intercepted and stopped by Israel’s navy. The point is to make this an international incident that puts pressure on Israel to at least lessen it’s genocidal tendencies. If all ships went at one time, it would be one news cycle. This way, they are making multiple news cycles out of it, maximizing the pressure.