The whole point of RICO prosecution is to make it easier to catch everyone involved in organized crime... especially those who planned it.
Sure we have Trump on tape asking to "find" votes he didn't have in order to overturn the election... but we all know that any MAGA on that jury would have jumped at the chance to acquit based on the vagueness of the language.
A RICO trial means that the jury will only have to be asked to find Trump's henchmen guilty for their parts... and that will be enough to damn Trump. MAGAs will probably do this, because their cult loyalty does not extend one inch beyond Trump himself.