Maybe she's just a Chud and did it on her own, but the trump kompromat angle makes sense as well:

1. She performs the Sunday night football song in a short dress and she's younger and blond - so there's a chance trump saw her and paid attention (because he's a rapist that likes girls with features similar to his daughter).

2. He probably asked his sycophants to get her for the inauguration or a rally or some stop on the garbage parade, have to assume she said no at first realizing the career backlash, if anything.

3. They scramble to find leverage, she was on American Idol, which is a former fox show (Murdoch) and a current ABC show (ABC being the complicit mainstream network to first bend the knee HARD recently, preemptively settling trump's defamation lawsuit against them with a huge multi million dollar payoff).

4. So between all of that, someone has the leverage against one of those remaining producers to get them to offer underwood the replacement "judge" job on American Idol, with the condition that she support trump publicly.

5. She was announced as a judge on American Idol.

6. She performs at the inauguration.

7. American Idol producers make public statements about fear of a backlash boycott, but say they won't do anything about her.

8. The purposefully convoluted threat of a boycott fuels fox and others , along with the fully complicit social media networks, to push a counter boycott - meaning all of the Braindead maga folks without anymore rallys to attend should now go HARD for American Idol, buy merch, etc.

9. Get now loyal viewers to send in their underpants as tribute. Collect all those underpants.

10. ???

11. Profit