From an objective standpoint, the known effects of Iridescent Mercury were rather marginal and niche. It saw minor use in certain expert mechs piloted by notable leaders and commanders.
Yet the allure of using other resonating exotics that improved a concrete combat-related priority was too great. Few expert pilots and mech designers valued the effects of Iridescent Mercury over the alternatives.
The situation was different here. Iridescent Mercury happened to resonate quite well with Venerable Joshua. This allowed him to derive greater value from this material than many other mech pilots.
What actually stole the show was Master Willix's unexpected discovery that Iridescent Mercury possessed highly complementary effects towards glows. She even presented a bold theory that explained why this might be the case.