Why the krogan were brought to andromeda?

People would have complained if they weren't. 

According to Nexus Uprising, the Nakmor clan was involved in building the Nexus (or maybe even the Arks). Jier Garson was impressed with them and go along with them. As a result, she invited them (specifically them, not krogan in general) to the AI. They were all builders, for the record.

I can second this

Everyone is bringing up they are the muscle. I think for the Initiative there is another major reason. The Krogan seem to adapt to harsh environments much better then any of the other races. Seems like when you are going someplace new that you have little idea of what you are going to find you would bring the most adaptive race with you. I doubt it says exactly that anywhere in the codex but it fits.

I think its because Krogan are ideal first pioneeres you want when settling unknown planets. They are very hard to kill - both by enemies and enviroment.

Addison's annoying but largely sticks to her own domain. Tann and whatshisface (Addison's peon) should be put out the airlock.

This is a good reason, however according to the AI plans, they were going to settle "golden worlds" that were already in pretty good shape. Still i could see the use of krogans as pioneers in certain hazardous locations that would help with exploring, mining, fighting off threats (wildlife or aliens), etc.  So yeah i can get behind that idea.

The other idea that is sometimes mentioned ingame as "they're muscle" didn't make much sense to me, that's why i made the thread. I haven't read the uprising novel yet, and i know that Kesh is an engineer, but if that was a big motivation, then it should have been expanded a lot more ingame. Like someone arguing with Tann and using some of these reasons.

It was quite disappointing to me that unlike in past games, the codex here provides very little in regards to clarification as to what is going on. The krogan entry says nothing about this, it's mostly about old milky way stuff that any trilogy player knows already. The relevant questions about the krogan in andromeda are just ignored.

Tann is a huge bigot.  He saw them as "dangerous krogan" first and engineers 1000th.  He's the kind of salarian who believes the genophage was not only the best idea ever but that it could feasibly be brought back fully working (it's starting to show weakness after 2000 (plus an extra 600 asleep) years).  Tann actually thought that he might eventually want to do so at some point - meaning soon, given the short life spans of salarians.  The three leaders of the Nexus in uprising were Tann, Addison and Sloane.  Don't trust a single one of them, Sloane mainly because her anger was ridiculous.  She's not a people person and that was seriously needed when tensions were flaring.

The "succession" is automated, predetermined before the AI launched. Tann's name seemingly appeared out of nowhere, based solely upon his seniority (as in early backer/sign-up) for the Initiative. I still wonder if his appointment was sabotage, an error or something else unintended. It's entirely possible that Addison would be next in line. It's also possible that yet another sleeper's name would appear.

Addison seemed surprised and dismayed to have been passed over when Tann's name appeared. She clearly seemed to believe that her senior leadership role was going to make her the obvious next step.  Sloane and Kesh could've guided her, so that likely would've worked out better, as useless as she was pre-Pathfinder.

I can tolerate the inconsistent characterization of Sloane, though I feel it was a mistake and a missed opportunity. The one that gets me the most is, "Many of the exiles were security". When Liam says that, I think, "Uh, what? I recall Sloane being the only security member exiled." The rest were engineers and random background characters. Some security personnel could've been exiled, but it felt like that would've been mentioned. Sloane getting taken in by her own people was a huge moment.

Similarly, on the computer terminal in some exiles' house (I don't recall on which planet), there are emails about being persuaded to join the rebellion that Sloane was starting... but in the book she not only doesn't start the uprising, but she was never part of it. She was literally in the wrong place at the wrong time, negotiating from the side of Nexus with the rebels, when the attack began. After killing a krogan in self-defense, she sticks with the future exiles to keep them from getting too out of control.