As this theory goes, "The disciples made the story up."
There are three simple counter arguments that debunk this foolish claim.
* In all honesty, this is hardly even an argument anymore, because it just is not plausible, if you give it serious thought. The disciples and early Christians willingly dying for a “conspiracy" just does not make sense at all. Nothing PROVES sincerity like martyrdom. As the saying goes, "Liars make poor martyrs." The dramatic change in their lives from fear to faith, despair to confidence, confusion to certitude, runaway cowardice to steadfast courage under threat and persecution, not only PROVES their sincerity, but testifies to some powerful cause of it.
* There also could be no possible motive for such a lie. Lies are always told for some selfish advantage. What advantage did the "conspirators" derive from their "lie"? They were hated, scorned, persecuted, excommunicated, imprisoned, tortured, exiled, crucified, boiled alive, roasted, beheaded, disemboweled, fed to lions, etc… There is no evidence that not even one recounted.
* If the Resurrection was a lie, and the Jews knew it to be, they would have produced the corpse and ended the feared superstition. All they had to do was go to the tomb and get it. The same goes for the Roman soldiers and their leaders. They also would have produced the corpse and ended the feared superstition.
This is not even an argument among scholars anymore. Scholars understand that the disciples did not come up with a conspiracy. Though scholars may not believe that Jesus rose from the dead, they can attest that Jesus body went missing, and that the Disciples lives were changed dramatically after the crucifixion claiming Resurrection.