It is not the function of the courts to investigate.
But it is their function to hear evidence, and to order additional evidence produced, if the early evidence meets the low standard of probable cause to believe...
They haven't heard any evidence, nor have they granted access to any other evidence that would be relevant to the case. What you are saying is that absolute proof is required. These have been civil cases where the actual standard should be preponderance of the evidence. But that's for final judgment, the standard for discovery is much lower.
“It is not the function of the courts to investigate.”
Very well and succinctly put.