I applied for the customer service representative role. They sent me the message asking for my transcript.

My concern is why we would pass the interview stage without a virtual interview, why so many people would pass the online assessment test (I know 23 people who applied and all 23 passed the assessment and got the message asking for their transcript) and why they would ask for transcript before the job offer.

As far as I know, they could also be selling people's information to bigger scam agencies that deal on jobs and scholarships. If they got your transcript, that's all they need to apply for funds using your identity.
They are Nigerians. It's a Nigerian scam group. Funny thing or not so funny is that some person's have admitted sending their transcripts and they haven't still had an acknowledgement from them.