The day after the crucifixion, the Cabal and the fundamentalists sent a delegation to Pilate. They said, "Your Eminence, we've been thinking: before he died, that poser said he would be alive again in 3 days. You'd better give orders to secure the tomb until those 3 days are past. His apprentices will probably steal the body and tell people he's alive. If they pull that off, things will be worse than before."
Pilate said, "If you want to waste your own security detail's time on this, go ahead."
So they sent their goons to seal off the grave site.
Matthew's version of the resurrection story is the only one that begins in the days before. While other gospels elaborate on post crucifixion appearances, Matthew's main concern is refuting the accusation that Jesus' followers are shysters and that the resurrection is a hoax, fake news, a scam.
Notice who is crying loudest about the possible competition for the hearts and minds of their constituency. It's not Pilate. Pilate is in charge, and has no reason to fear or second-guess his own authority or capacity. He may have been ruthless, but he was competent.
Instead, it's the cabal, nominally in charge, with no real authority of their own and a sense of their own superiority, importance, and righteousness who are afraid of what may come of people being given an alternative.
When it comes to authority, it's often those at the bottom, who are least secure in their position, who are the most ruthless about defending it. It's often the least competent, those with the least legitimate claims on the allegiance of their following, who are the most apt to cry "hoax" when things aren't going their way.
Some say follow the money. Matthew says, follow the fear.