Who betrayed Imam hussien. sunnis or shias?

thousands of people who took ' bayath ' on imam hussien and pledged to die with him for the sake of islam ( 70,000 to 80,000 ) but later turned away and leave the imam and his family in desert, are they sunnis ? meanwhile who is '' omar saad ''(cousin brother of imam hussien) who informed 'Obadullah ibn ziad' about the whereabouts of 'muslim bin aqeel' and 'hani ibn arwa' and gets reward for this act.does he a sunni ?you shias ( mutah people ) betrayed the imams, betrayed the prophet and '' defame '' your own imams by handmade fabricated stories.