When something falls to bits, it means that it is crumbling, deteriorating or breaking apart. Some synonyms for this phrase include falling apart, disintegrating, dissembling, decaying, breaking down, collapsing, failing, fracturing, crumbling down, and shattering. These words imply that whatever had once been whole is now fragmented or destroyed to some extent. Other appropriate synonyms for "fell to bits" could be dismantled, disassembled, disintegrated, or broken up. Whichever synonym is used, it describes a situation where something has completely fallen apart, lost its form, or no longer serves its intended purpose.