What is the ruling on someone who intended to stop the prayer while leading it due to the intrusive thought (waswasa) of showing off (riyaa'), but then completed it and re-prayed it alone, knowing that he did not stop it out of shyness and did not intend mockery?

The prayer becomes invalid by the intention to interrupt it, because the continuity of intention is a condition for the validity of prayer, and this is the view of the majority of scholars. The Imam who intended to interrupt his prayer for fear of showing off made a mistake, and he should have prioritized shyness before Allah over shyness before people. He must repent to Allah, and his obligation has been fulfilled by repeating the prayer he invalidated.