What happened to the Krogan?

This was a minor kett force, that was being distracted from its undivided attention. The kett is and will be more of a threat than the krogan that would only be so dangerous if all their clans were united in the rebellions (they were not; everything was just about expanding to more worlds as they grew in population, and clans had all sorts of politics - its very easy to consider that if the krogan rebelled now (post-ME3) that it'd still be a very hard fight but they'd be put down more easily than the staving off *for decades*).

The krogan are amazing at combat and population growth but besides the genophage event, they have many factors that keep them from an objective superiority in the galaxy.

In the OT, the point was more that the Citadel wasn't *ready to cope with an uplifted species*, not that this species was actually so much of an easy threat to the whole galaxy. You think the genophage was so hard? All sorts of other weapons could have and may have been produced. However, the galaxy was still grateful to the krogan for handling the rachni and there's plenty of evidence that they kept giving the krogan chance after chance, diplomacy attempt after diplomacy attempt, keeping conflicts smaller than they would have been, until the krogan managed to push their presence up to Palaven's moon. Then everyone went "Enough of this shit" and even instead of blasting the krogan to hell with advanced destructive weaponry, they employed the 'soft death' of the genophage.

The krogan were only going to take over the galaxy if the rest of the species kept soft-handing them, not because of some intrinsic weakness in the other species. Perhaps if things were 'one-on-one' any of the other species would lose, but you'd be missing the bigger picture that the krogan don't have the luxury of only dealing with species on-on-one, and even then, if the salarians could cook up the genophage, they could probably cook up much worse, and lacking useful scientists, the krogan would more likely just flop around and die out even faster than with the genophage.

Not quite surprising you're missing the bigger picture when looking at your Zaeed avatar though   (just a joke about Zaeed being the most willfully ignorant about pretty much anything, and just focused on how better to shoot things and immediately survive; I don't mean it personally as an insult)

The krogan are superior in a few roles: ground troops, territorial spread, utilization of technology for destruction, survivalism. None of this means they are 'top of the food chain'. In fact, turians staving them off for decades and salarians making a SOFT weapon of the genophage are themselves evidence that the krogan were being patronized on any larger scale than ground war, until it was enough and they got effectively neutered and made to mostly stay in their DMZ. All throughout this process, its likely the asari kept trying to push for peace because their space beyond border colonies were probably never even threatened in these decades.

I suppose if the galaxy was only the more historical salarians and asari, the krogan may have defeated them simply due to their quick expansion overwhelming any more soft approaches. But they were not dealing with just 'salarians' and 'asari'. They were dealing with the Council (asari and salarians in cooperation), with its minor races, and Turians on the scene and ready to unite as a people against the krogan.

The krogan have a reputation amongst themselves as ferocious warlords amongst themselves, but others view them as tool brutes, even the long-lived asari, for a reason. They were never an existential threat, but they were strong enough to present the eventual possibility of becoming one. Thus *genophage*.

take some Krogan and turn them into KettKrogan and fight Krogan with StrongerKrogan. See who wins that, while the Kett have better ships, technology, adherence to organization, etc etc etc? Maybe if all Krogan were in some endless blood rage something would get done I suppose. Not all Krogan are Wrex/Drack/Grunt. Not by far.