Evolution of hunting behavior of parasitoid wasps
Context is everything. Lets start by working back to front. 


  larvae eat the tarantula organs in a specific sequence to keep it
  alive as long as possible.


Most of the time if the larva eat the organs in the wrong order they don't die, they just end up with less food. It is pretty easy to see how this could evolve to be better, larva that eat in the correct sequence end up with more food thus have an advantage, larva that eat in hte absolute wrong sequence don't survive.  


  on a [specific] species of tarantula


Again easy many wasps are not as picky they will lay their eggs in/on a wide variety of hosts, but specialization is favored a lot in evolution as it helps your lineage exploit a resource better and better, you only have to deal with the defenses of a single species as opposed to many different ones which might have mutually exclusive solutions. 


  lay their eggs in a specific region.


again failing to do this does not necessarily mean their larva die, it just means they are worse off becasue they don't get to eat as much. Again easy to see how this evolves, a wasp that picks its target end up with more well fed offspring. Many don't even lay their eggs inside the host but outside and let them eat the host from the outside in, this is what this species does.


  Upon finding a tarantula, the wasp locks its mandibles onto a foreleg and brings its stinger into position so as to paralyze it.


Again not every parasitic wasp does this many don't paralyse their host, but they jab them with the ovipositor relying in brute force to injure, paralyse, or kill the host. Others just lay their eggs on them and fly away. Others simply kill the host jam it in a hole and lay their eggs on it. But wasps that paralyse the host are less likely to get attacked. but even if they kill the host instead the larva still get a meal. hunting always tends to be risky, but as long as the reward outweighs the risk it can evolve. Additionally many wasps do not target adults but larva and eggs that can't fight back. venomous Stinging is actually fairly rare in wasps occuring only in the ones that attack the most dangerous hosts. Of course once a wasp lineage gets good ant not killing its host then there is little reason for the larva to be able to eat more putrid remains of the host, as such adaptations are costly so you can see how after they stop killing the prey the larva might lose the ability to keep eating dead hosts. 


  The wasp then drags the tarantula into a hole that it has already dug.


Again not every species does this, some just lay their eggs on a host, without doing anything else, but this carries more risk of your larva getting dislodged or injured, but insects are not people if there is a parasite on their back there is not a lot they can do about it. 


  These wasps are solitary, which means there are no conspecifics to
  teach the new wasp how to do all this. Thus, the entire behavioral
  program described above must be encoded in the wasp's genome.


Even your own source disagrees with this, it shows wasps get better at subduing the host the more often they do it, laying eggs in NOT a once in lifetime thing they may do it many many times, so not being perfect can still work. 

Once you see the huge variety in parasitic wasp behavior it is much easier to the step by step sequence that can happen to get to each one. You are not even at the most extreme, there are wasps that go even further, like having viral mutualists, larva that can't poop so as not to contaminate a host they live inside, and even leaving chemical markers to keep other wasps from laying eggs in/on the same host. Parasitic wasps are rather well studied I invite you to look more into them, they are really good models of evolution.