Congress is responsible for certifying the presidential election - not the courts. HOW Congress does it, or what level of evidence they require, is left to Congress.
That pesky Constitution doesn’t leave it for the courts to decide the outcome of the presidential election.
Just out of curiosity, if Congress certified the election of somebody you personally knew for a fact was not Constitutionally eligible, would you consider that person a lawful holder of the office?
We have checks and balances in this country. If Congress fails to do its job in accordance with the Constitution, courts declare their actions unConstitutional.
That pesky Constitution doesnt leave it for the courts to decide the outcome of the presidential election.
The Constitution doesn't bar them from overturning fraud in a national election. They are given the responsibility of judicial power over all Controversies to which the United States is a party. IOW, if Congress messes up, the court has judicial power to make them fix it.