The Obama administration shut down and buried the previous FTC investigation. I'd guess not just because of lobbying, but also because google was nice enough to allow a ton of google employees to take some "vacations" to work for the Obama campaign for a bunch of months, and the likes of Eric Schmidt being chummy with Obama[1].
The current investigation is probably motivated not just by those career bureaucrats who had their previous investigation shut down, but also by the Trump administration wanting to hurt SV and Google in particular for being too friendly with Democrats, and to put those social media companies (Youtube, Facebook, Twitter) on notice not to "prosecute" and ban conservatives on their platforms (at leas that's what Trump and a lot of "conservatives" say is happening).
Google's close ties with the Obama administration makes the Trump administration suspicious!