I don't know how connected you are with Bangladeshi politics right now, but poll-hacking through extreme repression is the first trick Sheikh Hasina/her party Awami League mastered. I am not surprised to see such a high approval rating, rather, I'm surprised to see 30% people signal disapproval in an environment with extreme political speech suppression. If you doubt that, read the story we're discussing under again. This is a government that's been jailing people without trial for their Facebook posts.
If you want to know some indication of the true feeling of the people, go check out the Facebook posts of anything related to the ruling party, and check the ratio of "haha" reacts to likes or hearts. Generally, that's 4:1 in my experience.