If I block a 5/5 attacked with a 2/3 during my blocking step, could I then bounce my blocker with Acrobatic Maneuver and prevent it from being killed, while also having the 5/5 blocked? If so, why?
When a creature becomes blocked, it stays blocked and blocked creatures do not (normally) do damage to the player.
509.1h An attacking creature with one or more creatures declared as blockers for it becomes a blocked creature; one with no creatures declared as blockers for it becomes an unblocked creature. This remains unchanged until the creature is removed from combat, an effect says that it becomes blocked or unblocked, or the combat phase ends, whichever comes first. A creature remains blocked even if all the creatures blocking it are removed from combat.
Lore-wise, think of the blocker as having delayed/distracted the attacking creature long enough for it to not reach you.