if anything, STG moving to upgrade so quickly shows how much they probably regret that uplift. If not that, then it shows a much darker side to their own culture considering the only race ever aware of the Genophage starting to weaken was the Salarians.
Alternatively, it demonstrates how much "maintaining the genophage" in and of itself - regardless of the consequences - had become valuable to elements of the salarian elite. It seems apparent to me that many Council observers consider the genophage to be their sole safeguard against a metaphorical avalanche of bloodthirsty krogan. They equate the end of the genophage to the end of their security, instead of seeing it as only one part of an entire network of measures taken to limit the security threat that the krogan posed.
It's important to remember that the genophage was not an immediate-impact superweapon that instantly halted krogan offensives. By definition, it's something that would have a very gradual effect. All it did was modify birth rates: nobody would even be able to tell whether it was working for a generation. It had no effect whatsoever on the krogan armies and fleets that already existed. Primarch Victus claimed that Menae was where the turians made their 'last stand' during the rebellions, and that the genophage was what saved them. This is flat-out wrong, directly contradicted by the planet descriptions in the Apien Crest and indirectly contradicted by common sense.
A more accurate description of the genophage would be a comparison to the turian bomb in the Kelphic Valley. It was effectively a fail-safe, designed to
secure a military victory over the krogan clans that Council forces had already won. Because nation-building on Tuchanka was presumably deemed too expensive, risky, and difficult, the Council elected to militarily neuter the krogan and live with the relatively minor consequences of the societal instability that the genophage caused.
Eh I don't think the problem was the use of the Genophage to stop the rebellion but its continued use without any consideration for the psychological damaged it caused and overall stagnation of the Krogan's societal development by the galaxies "elite".
I strongly agree, and I think that that was one of the primary takeaways that was intended by Mordin's loyalty mission. (In ME3, Bakara hammers this point home.) Mordin made several arguments based on projections and threat assessments, and the construction of theoretical scenarios revolving around responses to the end of the genophage. And, y'know, if the only issue was the objective population threshold and the birth rate, he'd have had a fairly good argument. Confronting him with the evidence of the dead krogan test subjects showed him that there were other consequences to leaving the genophage in place.
Threat assessments and projections are notoriously dubious anyway. Any prediction of the future relies far more on the prejudices of the predictor than on some objective extrapolation. Tetlock and Belkin's famous study of academic predictions over the last several decades demonstrates this rather nicely: even "fox" prediction strategies aren't that useful, especially when applied to all of history. (Too many variables! Too many variables!) What's the likelihood that salarian projections took the effect of the genophage on krogan psychology seriously? It's gotta be pretty low, right? Especially given Mordin's response to it? The salarians took what they thought they knew about krogan bloodthirstiness and military instincts and incorporated
those assumptions into their models.
The same caveats, naturally, apply to what Maelon thought would happen if the genophage was ended. He thought that the krogan would undergo some sort of cultural renaissance. There's no particular reason to assume that that would be the case, either: the way Clan Weyrloc treats his genophage cure indicates that there are plenty of krogan all too interested in using the genophage for wars of conquest and revenge. Even though the almost total lack of krogan space-naval assets means that such wars would be hilariously one-sided, either way a "renaissance" seems awfully unlikely. Theoretically possible, but unlikely. The factors that made that renaissance possible in ME3 - Wrex's leadership, Eve's presence, the threat of the Reapers - weren't in the picture when Maelon was running his experiments.
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Eve's suggestion that much of krogan violence stems from the psychological impact of the genophage has a fair amount of weight. Obviously, we don't have anything like a longitudinal study of krogan motivations going back over the past millennium and a half. But from what we know - the krogan we encounter - the genophage casts a very long shadow over almost everything they do. It is virtually all-pervasive, which makes sense, because it affects every krogan. How could it fail to have had some sort of impact on the way they think about their place in the galaxy? Even something as minor as the romance between Ereba and Charr: one of the reasons she has problems committing to him is her suspicion that he's just using her as a baby factory because the genophage makes having krogan children fantastically unlikely.
The genophage also has a more
obviously negative societal impact in that it dramatically shifts the dynamic of clan warfare. Urdnot's scout commander makes it quite plain that because of the genophage, women and children are in relatively short supply, and losing them has a very disproportionate effect on a clan. They're simply too juicy a target to pass up. As Clausewitz might say, for
any given krogan clan, the women and children are the
Schwerpunkt, the "center of gravity"...and for Clausewitz, attacking the enemy's center of gravity was the most effective way to fight a war. The scout commander doesn't quite put it in those terms: he simply says that for a clan to lose its women and children is to lose its future. I don't know about you, but most people think that transforming warfare into a game of directly attacking noncombatants is
horrifying.
Then again, if you're
the kind of person who thinks that the krogan should have been slaughtered en masse in retaliation for the rebellions, then you probably aren't all that worried about the societal effects of the genophage on the krogan.