Don't you think they are three former world champions who have been completely forgotten and underestimated?
I liked Glowacki a lot - a sort of deluxe brawler. I liked Artem too but I thought he was good for a bit more. In the end though, these guys are just belt holders. Flood the market with belt holders, of course many of them will be forgotten. There might be 60 belt holders in the world right now, 60 next year, 60 the year after…
But the problem if these boxers have not a world belt they will be more forgotten currently you don't think so ? Some peoples will never think about them or watchs their championships fights if they was not world champion... Glowacki is maybe the world champion of the last years who is the most underrated in Cruserweigh category. Both styles of Artem Dalakian & Daniel Ponce De Leon was very amazing and something like unique, Artem Dalakian looks like a Prince Nassem 2.0 but different and Daniel Ponce De Leon was a brutal Mexican southpaw / pressure and puncher he was unique in Mexico we don't have a similar profile currently.
“Three former world champions who have been completely forgotten.” Your question was about why, despite being world champs, they’ve been forgotten. My answer is, if “champions” are about as common as contenders, they’ll be as widely remembered as a contender in some instances (including these). Every contender from the 1960s is not well remembered.