Why not? Because it all happened too fucking fast.
All three of them just happened to be right on top of the stargate as soon as it dropped out of FTL? Why wasn't anyone out gathering food or water? Or taking a bath? Or patrolling the area? Or performing any other activity that stranded people would be performing? But no, they were right at the gate, all packed up and ready to go.
Who said they haven't started doing those things? Just because they have doesn't mean the three wouldn't ever be at camp together.
Why were the aliens comfortably parked there moments later?
How do you know they were there just moments later? A good bit of time had passed in between the trio gating to Destiny and them sending the Kino back. It could have easily been a few hours, given what had transpired on Destiny in that time. There was no way to tell how long they'd been waiting there. They could have arrived just minutes before they sent the Kino, for all we know.
How or why did they find that particular stargate so quickly when, as we clearly saw last week, they never seemed to bother with any of the other gates the Destiny had been in range of when she stopped?
I'm not a writer for the show, so I can't tell you.
Why would they just be parked there? What exactly were they waiting for?
The humans, maybe? The aliens knew they were there recently, if for no other reason because they found the camp. And since they knew the ship was adrift due to their sabotage, they probably figured the humans would consider evacuating to the planet.
Why was Eli so annoyed by the act of sending a Kino back, especially if it was, in fact, standard operating procedures since they've been onboard? Which translates to "we do this every time we go back to a planet, even when gathering supplies." Which, in turn, means he's done it several times before. And considering it only takes a moment, why would he be annoyed by the idea anyway? It's not like he wouldn't send one through normally even if it wasn't the normal procedure. He's a Kino freak.
I saw it as being done for dramatic effect. Remember, he does whatever the script says, not necessarily what would make sense. Though I admit it does seem a bit fishy now that you explained it more.
Why were all three of them so passe about getting back? There was a "hey, we made it back!" bit, but then it was business as usual. I don't know about you, but if *I* thought I was stranded forever, I'd be way more freaked out about everything that happened. Both positively and negatively. I wouldn't be just "hey guys, how's it going?" and then go about my normal routine.
I agree their reaction is unusual. But you're assuming that fictional characters must react like real people would. That's wishful thinking. They only say what the script tells them to say, not necessarily what makes sense.
Dismiss all of that if you want to.
I don't see much concrete stuff
to dismiss. Crazy coincidences, unrealistic dialogue and actions occurring without any good explanation are just par for the course for shows like Stargate.
But I'm sure as fuck not going to.
No one is saying you should.