Why has the cruiserweight division lacked competition since the 90s?

The cruiserweight division was established in the 1980s (actually the first title fight took place in 1979) as a division for 'small heavyweights', though many of the cruiserweights in the 1980s (like Dwight Muhammad Qawi) were essentially 'huge light heavyweights'. The decade of 1980s saw an intense rivalry between the rising Evander Holyfield and the more experienced Qawi. Holyfield became the undisputed champion at cruiserweight and moved upwards to heavyweight where he earned most of his better known success. Unfortunately though, the division could (arguably) never find such high level of competition since the 1990s. Yes, there have been some big names - Oleksandr Usyk is the first name that comes to mind, he won titles at both cruiserweight and heavyweight (Holyfield and Haye have also done this). Other known names are Virgil Hill, James Toney, David Haye and Marco Huck. Of all the names mentioned, only Holyfield, Qawi and Oleksandr Usyk can be named as true all time greats of the division (Toney's main exploits were elsewhere). I am not even sure if ten cruiserweight champions would feature among the hundred best pound for pound boxers of the last fifty years.

The cruiserweight class is broad - it spans over twenty five pounds. It is in fact the class with the biggest range (ignoring minimumweight and heavyweight which have only one limit). And yet, action in the division has been sparse over the last three decades. Understandably, there is a lure for cruiserweights to move upwards to the more lucrative heavyweight division. But could this be the only reason why we have not seen a true great rivalry in the division since Holyfield-Qawi?