Basically, their claims about similarity of the Wuhan virus to HIV were wildly disproportionate to the evidence they presented. They performed a very shallow analysis and found a few short regions within a couple proteins that appeared to align to HIV proteins. The alignments were so short that they were very likely spurious, however.
They took these inconclusive results and then wildly over-intepreted them with sensational language. The whole thing was a giant irresponsible embarrassment that should have never happened.
If it sounds like I’m kinda piqued about this, it’s because I am. This awful manuscript managed to spawn wild conspiracy theories all over the internet. Thankfully, the authors at least acted responsibly enough to withdraw the manuscript after it received a bunch of valid criticism. But the damage was done.