FTC/DOJ/FCC have different, and sometimes complementary, powers. DOJ is taking lead on Google right now, but don't forget FTC just fined Facebook $5B. DOJ may be at the forefront of this particular action because of Trump's grievances, but there's no reason to think Biden wouldn't go even harder, especially if we get Pai out of the FTC (praise be the day). GDPR has been a total wash, it will be funny to see the Americans actually do a better job with a far more constricted legal toolkit.
I would be incredibly surprised, Harris was advised by Jonathan Mayer on privacy issues, the Democratic House just released a scathing report on tech monopolies, and Biden knows he still needs support from the Sanders/Warren crowd who are salivating at the prospect of breaking up Big Tech. Facebook's shameless support of the Trump admin may likewise be viewed as one of many of Zuck's poorly thought out moves. Unlike Obama, who credited Facebook/Google with his 2008 victory, and opened a revolving door between Google/White House, the appearance of that would be absolutely toxic in the present climate.
My largest issue with the Obama administration was their incredibly corrupt and cozy relationship with Google. It's one of the reasons I was really hoping nearly anyone else would win the primary.
So yeah, I wouldn't be surprised if Biden drops it, but only because he was likely part of the problem to begin with. Google wouldn't be the problem it is today if the Obama/Biden administration was doing their job.
(Still voting for him, mind you. It's not like we have better options.)
But basically, a massive number of Google employees were installed in high-level positions of the Obama administration, and a lot of Obama administration folks got great jobs at Google. Obama installed a professor who wrote studies about how Google shouldn't face antitrust scrutiny (who was paid by Google to do so) as the FTC Commissioner (Joshua Wright, who is now a lawyer at Google's preferred law firm... he went from Google shill to government official and now back to Google work), and an FTC case against Google where staffers recommended litigation inexplicably got shoved under the rug.
Then you'd see things like a former Googler in Obama's administration announce an initiative to budget billions of taxpayer dollars to buy computers for schoolchildren... unshockingly, these were intended to be Chromebooks, which get kids started early as Google account holders. (I believe Congress ended up rejecting this particular budgetary line item, or reducing it significantly.)
This sort of topic gets a lot of people going on both sides of the matter, and people get very loyal to their camps. Accuracy often has nothing to do with how people vote on these things. We've got an intersection of partisan US politics and Google here, it's voting catnip.
(Bear in mind, my post both speaks ill of Obama, who might as well be Jesus to the Democratic Party, and also made it clear I'm voting against Trump. So I ingratiate myself with very few politically in the parent comment.)
That's usually how this stuff works.
> And why didn't Facebook get sued too
You can't make one case against multiple companies, and resources are finite. It will take many years for each of these cases to play out.