If there was insufficient evidence to bring a case, the prosecution wouldn't attempt a trial. I don't know where you live but in the US prosecutors, both on federal and state levels, weigh the viability of trying a case as one's conviction rate is considered important. And on such a high-profile case, it's career suicide to bring a frivolous case.
How much time has passed is irrelevant as this case centers on defamation by Trump against Carroll as it pertains to the rape and which occurred during his presidency.
As for evidence, her lawyers wanted Trump to submit a DNA sample to compare against the clothing Carroll claims she was wearing at the time of the rape and that has not been laundered. He refused to comply.