The problem is manifold:
Kavanaugh is up for the highest legal office in the land but has not demonstrated 'judicial temperament' which is essential in that role
his own diaries testify against him, and forced him to lie about their meaning (terms like "barf" and "Devil's Triangle" were redefined by him)
as this is not a criminal trial, but a job nomination, different standards apply
'hard evidence' is almost impossible to provide in a case like this - if the accusation is true, you can understand why Ford tried to mentally bury it
why haven't any of Trump's other Supreme Court nominees come under attack in similar ways? It this was political, they would have been without doubt.
I agree that it would be nigh on impossible to now bring criminal charges, but not to repudiate the nomination; let's not forget that Kavanaugh was a mere law clerk until promoted by Bush for political reasons (repaying favours? Not sure.) - further investigation may or may not be appropriate, the FBI seem to think not.