Shaikh Ibn ul-‘Uthaymeen rahimahullah said:

“If the Imam leads the congregation and he is one who broke his wudu but forgot that he did and he does not remember it until after the prayer, then it is obligatory for him to repeat the prayer. As for those praying behind him, then it is not obligatory upon them to repeat the prayer…”

[Fatawa Noor ‘ala Darb (2/8)]

And Allah Knows Best

Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan