Did tyrants develop democracy in Greece?

Tyrants usually preceded democracy. They were appointed in various cities by popular will to get rid of the aristocratic cliques and run a city-state to the general benefit of the people rather than the vested interested of a few. A tyrant had to maintain a bodyguard to protect himself from the aristocrats, and to hire them had to impose a tax on the people, which eventually made the tyrant as unpopular as the aristocrats had been. So the cities progressively expelled the tyrants and some tried the experiment with democracy - with mixed success.

Failures with democracy resulted in some cases in a return to aristocrats, monarchs or tyrants to sort out the mess. Most cities then turned to a compromise of a form of limited democracy where the magistrates allowed the people to vote yes or no on issues they put before them.

No. The tyrants in Ancient Greece were autocrats in Athens who stripped away much of the democracy that had previously existed there.