>>7384021you should read the short story as it is even better than the episode, but there is no proper answer
The answer in short: we do not know what the spider wants, it just seems to be part of a benevolent alien species.
In the short story the Milky Way and even places outside it are full of these travel gates which function as wormholes, however the system broke down a long time ago and only small clusters a few hundred light years across stayed connected, so you cannot use it to travel domain to domain. For humanity this means that the Aquila Rift is as far as you can get using them. However, as it turns out these disconnected clusters are still connected to a travel gate outside the galaxy in the Large Magellanic Cloud some 163k light years away, using which you can still cross domains, but due to the distance it takes hundreds of years. The protagonist of the story is the first human to accidentally discover this fact, and that 150 years passed back on Earth (and decades for him) when he wakes up. There is also an enormous amount of other aliens who suffered the same fate as one would expect. It is not explained why no one has used this connection point to colonize multiple gate clusters, but it is very likely that the insect thingies will not let anyone return home with the knowledge.
