Another bizarre one is Alexander Miroshnichenko. He was a world class am who won a bronze medal and beat Lennox Lewis. He won twenty+ fights then fought Oleg Maskaev in his professional debut. Maskaev won and he never fought again.
Kirkland didn’t disappear he had his Glass Jaw shattered over and over. Someone who disappeared was Sultan Ibragimov.
I thought he did well, he just happened to fight in an era with great HWs. Today he would be a dominant champ. Maybe only losing to Fury, maybe.
Isal - after beating Michael Moorer, Tua spent his thirties in a wasteland from which he virtually never returned He even turned down a fight against Wlad for the HW crown
Yoan Pablo Hernandez stands out in my memory, in terms of boxers falling off the face of the earth. Remember him being in some entertaining fights with Cunningham, and given hometown pressies vs Ross, and then not a peep around 2014. The man's only 34 as we speak.