> The real loss is Senators no longer trusting Alphabet/Google after this snub.
The Senators that wanted Larry or Sundar to voluntarily submit to and draw more media attention to their spectacle of abuse directed at the firm (and others in the industry) obviously didn't trust Google in the first place, and the rest know the game and aren't going to be effected by this except perhaps by realizing that Google's leadership isn't completely braindead politically.
There was no possible net upside for Google participating in the charade of a hearing, and the committee rejecting Google's offer of the most qualified person to address the substantive questions notionally at issue in response to the voluntary invitation for participation was an unmistakable signal that that was the case.
> You really don't want to turn the government against you.
You also don't want to voluntarily cooperate with the parts of the government that have already turned against you and are trying to scapegoat you to build support for policies hostile to your interests.
Law enforcement isn't the only part of government that can seemingly innocently invite you to talk with malign intent, and it's not the only part of government you should decline voluntary cooperation with when you don't have good reason to believe that the intent of the invitation is aligned with your interests.