Apparently Colby lost because the ref was bias toward Usman, he didn't actually get knocked down but slipped, and just read his take on the 5th round
“Let’s talk about the fifth round,” Covington said. “I’m beating his ass again. I’ve won the whole entire fight. The fight is mine. They’re about to wrap the welterweight championship around my waist. Then all of a sudden, I slip on a banana peel and I’m getting hit in the back of the head. Marc Goddard is seeing this right in front of his face. I’m getting hit in the back in the head."
I think Usman broke that man's brain
Colby Covington: UFC 245 loss due to fake fouls, referee missteps and slipping 'on a banana peel'
“Let’s talk about the fifth round,” Covington said. “I’m beating his ass again. I’ve won the whole entire fight. The fight is mine. They’re about to wrap the welterweight championship around my waist. Then all of a sudden, I slip on a banana peel and I’m getting hit in the back of the head. Marc Goddard is seeing this right in front of his face. I’m getting hit in the back in the head."
I think Usman broke that man's brain
Colby Covington: UFC 245 loss due to fake fouls, referee missteps and slipping 'on a banana peel'