First, it is heavily debated whether Ophelia committed suicide or accidentally drowned in the brook. With regards to her funeral, debate may circle around Hamlet showing his true love for Ophelia by jumping into her grave. He has been acting strangely--so much so that most think he has gone mad. When he realizes Ophelia is dead, his madness seems to have disappeared. Perhaps this is what sets Hamlet into another realm of insanity and/or revenge-driven madness.