Ended up with a bunch of traps, where two are on the same anchor (drag, drowner, etc.). What's the rationale behind this?

Depends on what they are, possibly for the mafia set!
Colt

Let me rephrase my question:

Why would you want both sets tethered together, such that if one connects, the animal takes the other set with?

That's just how the mafia set is made,it's a 2 trap set made for one catch! But like Jeff said it could also be for independent drowned trap on one anchor, if your saying that the traps a fastened in such a way as this wouldn't work besides the mafia set I have no idea way you'd want it like that! Maybe a youngan messing aroumd?

Sounds like they are set up for walk through sets.

Some like two traps at a set,but I believe,in most situations,especially when using drags,it's better to have one trap to an anchor.Often,the second trap remains set and can make another catch.Some trappers may not have enough drags to put one on each trap.It's a little bit of corner cutting but I don't think it's ideal.

I think in one of Boddickers studies, he found a catch rate increase of 30% on sets made with 2 traps. Do I do it all the time? Nope.

Always wanted to try um on my blind cat and yote sets, but it illegal here.i know if it's built right, it's tuff get 4 feet over 1 trap it be real tuff through 2!
Colt

I'll occasionally clip two traps into the same cable tie off for cat walk-thru sets if there's only one anchor tree/brush, etc. Likelihood of catching two in the same location (on a 48hr check) is very low, so I'm Ok with having the other trap serve as a "drag". Cats don't typically fight the trap much, so once they tetherball around something they usually just sit there. Not really my go-to setup though.

Personally, I've never liked doing it. Way more often than not, I end up with one trap on a critter and the ther trap sprung and laying in the dirt. I've alway thought that second trap would be better used at a different set, but again, that's just me.

Sorry, I didn't answer your question. My memory ain't what it used to be and at times I can get a little off track between reading and posting. I think the other guys answered your question for you.