Who is Ekrem Imamoglu, Erdogan's main rival, and why was he arrested?

Who is Ekrem Imamoglu, Erdogan's main rival, and why was he arrested? https://ift.tt/nh9Cl1d Ekrem Imamoglu, the mayor of Istanbul and a popular figure, had boasted jokingly that he was the only person to have beaten Recep Tayyip Erdogan’s ruling party in three local elections https://ift.tt/r9Hj7ia