I don't believe their pleas are indicative of guilt-- I believe they're guilty because we all saw Sidney Powell on television telling outrageous lies and making pleas for an electoral defeat to be overturned without grounds.You are choosing to believe their guilty pleas are indicative of genuine guilt, and that any testimony that doesn't condemn Trump would be to protect him, but it is entirely possible for their honest testimony to not actually help convict Trump.
The guilty plea is indicative that she knows she be cannot successfully defend her actions in court, and she'd rather assist the prosecution in exchange for leniency.