Flynn can withdraw his guilty plea and have a full blown trial. If that happens Powell can subpoena anyone involved and cross examine them under oath. She could bring in Strzok, Comey, any and all of these felons to get to the bottom of this plot.
They are trying to get the case thrown out by the judge for misconduct by prosecutors or dropped by DOJ so they don't have to disclose exculpatory evidence. Trials are too unpredictable and expensive.