Poseidon believed Hades stole the master bolt due to their past conflicts and Hades' reputation as a troublemaker and manipulator.
Poseidon believed Hades stole the master bolt because Hades was known to be a troublemaker and had a history of causing chaos.
Poseidon also had a longstanding feud with Hades and may have suspected him based on their past conflicts.
Additionally, Hades had a reputation for being cunning and manipulative, which may have further convinced Poseidon of his guilt.