Chris L'Etoile elaborated on the relationship between the Council and humanity ( years after he stopped working on Mass Effect even ) in a post on another forum. Some of that conversation is relevant here. I'll try to provide some context and hopefully the formatting doesn't blow up 
[Humanity is special]
But it's all from the humans, and they can't back it up.
The Alliance is a "Third Galaxy" power, and as a species humans are weaker and softer than the krogan, less wise and less biotic than the asari, slower and less intelligent than than the salarians, and less organized and disciplined than the turians. If they try to seize power in the ME1 ending, the result is a galaxy with a lot more prejudice against them and brushfire wars breaking out everywhere (listen to the news on the Citadel).
[Humans defeated the turians]
By responding quickly and with force. The turians outnumbered them by thousands to one.
[Other races fear humanity as a result]
They s*%# themselves because they realized, "Oh f*%#, the turians are going to pound these yokels into the stone age, and we haven't even had a chance to talk to them yet." The turians only understand total war - complete commitment of all state resources until the enemy lies prostrate and offers unconditional surrender. The human counterattack, without our knowing it, had just provoked that level of threat response.
The Council intervened to save us, not the turians.
Or at least that was the way I left it. ME3 could spin it differently - in which case that would be canon, and I'd be talking out of my ass more than usual.

[The codex says how awesome humans are (carriers, mobility, small military %)]
All true. But remember that their population and resources are roughly equal to those of the elcor. The problem is, if they mobilize there's real potential for a war of Krogan Rebellions level savagery. Neither the turians nor the humans know when to swallow their pride and walk away.
I think you're confusing something. The humans have no advantages of economy or biology. All they have is the hunger of youth. Council Space is complacent. They're wealthy beyond measure and untouchably powerful. They don't need to work for anything, they're coasting on the profits of their earlier investments. They've made it. The Alliance is like the Imperial Germany before WWI. "We'll do anything to share the prestige of our older neighbors, even if it means getting into a naval race we can't afford with the British and colonizing the crap islands in the Pacific that no one else wanted!"
[The aliens fleets were useless, humans saved the Citadel in ME1]
That's not quite accurate. The Council Fleet isn't useless - it's scattered. The Council peacekeeping fleets couldn't respond because they're out policing half the galaxy. It take time to organize and reorient for a counterattack. Meantime we only have a handfull of colonization clusters to defend, so we keep all our forces in a few big clumps. One of which was real close to the Citadel relay.
God damn I miss Chris' vision of Mass Effect.