Actually, Lisa wasn't fine as task manager, wasn't fine as a leader, knew she wasn't ready to manage a task but let herself be talked into doing so...and pretty much conceded all of that, which was one of the things Trump didn't like.

When your team loses, either monetarily or via decision like this one...it doesn't matter if it's by alot or a little. A loss is a loss and somebody has to be fired. But...from what I recall of the episode, they lost by more than a little. I remember discussions that children had no concept of 'shy', and that the print was WAY too small for a children's book. Lisa could have blamed Dionne & Star for both these things, which then could've been thrown back at her for ok-ing both as task manager.

Which is why the Boardroom decision usually comes down to personalities and passion and how you scratch & claw your way out of a corner. Holly Robinson lost every task she managed last season and still managed to make it to the final two because of how she fought in the Boardroom. Trump wants to see passion and fight and wants a candidate to convince him WHY they should stay and/or somebody else should go. He does not want to see somebody admitting they weren't ready and didn't do well in controlling their team.