This is pure speculation.
Much less so than Edison "luring" his victims to the place.
Nothing in the movie ever suggests this is in any way some kind of known 'mysterious' place that people want to explore.
Except for the direct statements to that effect?
Kirk is supposed to be the first-ever party known to UFP to venture into the rubble nebula. This supposedly before anybody ever hears of Altamid or crashed ships or whatnot - else why is Kirk assigned to Yorktown, a station placed right next to the nebula (i mean a walking distance!) and therefore absolutely necessarily existing because of the nebula, in a ship that uniquely is supposed to be capable of braving the nebula?
Distress signals? Mimicking intriguing readings? There's plenty of stuff we've seen before in Star Trek that could easily draw in anyone passing close to the nebula.
But the UFP is aware of no such thing. The mystery of Altamid is not that it's sending out mystery signals. It's that nobody, to the best knowledge of the UFP, has been there or can tell what lies within the nebula. And this is impossible if nobody inside is eating ships, because we clearly see getting in is no ordeal whatsoever.
He sent an extra lure to Kirk because Kirk wasn't going anywhere near the nebula on his own.
Except for already being in the nebula. Or twenty paces from it, which is the same thing.
We see like a few dozen people at most outside Krall's power, not many more inside it. And a handful of ships, which could just as easily have been captured and brought back for spare parts.
And we see Krall's hunger. The guy is snacking on Kirk's crew like crazy - at the minimum demonstrated rate of six people within the adventure, he must have been "luring in" tens of thousands since the 2160s at the very least.
Nothing in the movie suggests that Krall would be taking ships in sparingly, or that there would be very few of them.
You have completely and totally misinterpreted what the movie says about the nebula.
Oh, I think it's vice versa. The nebula is up front and in your face in the movie - an immense presence that drives not just the whole adventure but is also the center of Starfleet interests there. They have built a giant space station right next to it, out of all the places in the universe. They have yet to properly survey it, but an effort is ongoing with the Magellan probes. If they could just Google the contents, none of this would happen.
Yet great emphasis is placed on the nebula being no obstacle in the end. It cannot stop Edison from mounting his crusade. It doesn't slow down Edison's old ship, either. It is not quoted as a factor in the fates of Jaylah and her family, or those other castaways. Heck, it's not even claimed to be the reason of the fake crash of "Kalara" and her ship.
Yet nobody knows of Altamid. The place is very much a mystery, central to the movie. To miss that is to miss the entire story.
Timo Saloniemi