Reb Moshe was unwilling to make statements about HKB”H’s calculations for how He runs the world and why He makes things happen… I can accept that a Talmid Chochom, such as Reb Moshe was, could possess Ruach Hakodesh, and could be privy to HKBH’s master plan beyond what is accessible to us mortals. But that neither gives him the authority to divulge this…
Reb Moshe, for his reasons, may have chosen not to attribute specific tragedies to specific causes. Other Geodlei Yisroel zt’l have indeed made such specific attributions. Each of these Gedolim had their own cheshbonos in deciding whether or not and what to attribute it to. And the Gedolim who have, in fact, attributed tragedies to specific causes are far wiser and more steeped in Torah and the ways of Hashem than any of us here to dare challenge them.