As far as I've been able to tell, the evidence for pangolins as the vector for Covid is somewhat circumstantial at the moment, based largely on their presence in the Wuhan wet market that has been implicated in early spread, a history of pangolins being found to carry and transmit various coronaviruses similar to Covid-19, and some specifically suspicious test results in pangolins from the market. Nothing specifically causative that I've seen (AFAIK, the link to the wet market as the source rather than an early transmission location isn't even well-established).

I suspect that, given we're a year on from the initial transmission of the virus in humans, unless the Chinese government has more research they haven't made public, we'll likely never know the truth.