They were a mixed race couple and it was unconventional for them to be married. Desdemonas dad disowned her because he was furious.
Othello and desdemona get sent to cyprus.
Desdemona is killed
Wants to make Othello believe Desdomona cheated on him. All about revenge because Othello did not promote him.
Iago was lying
Bianca brings Cassio back the handkerchief that she found in his things, The handkerchief was stolen from Desdemona by Emilia and planted in Cassios things by Iago to make the story that Cassio and Desdemona were having an affair believable
After some time Othello became more and more angry leading up to him killing Desdemona because he did not believe that she was telling the truth about not cheating
In the end it comes out that Iago was lying the whole time