You don't think there's any political reason they are going after Amazon rather than, say, the New York Times? Just the impartial watchmen of Democracy studiously promoting the adherence to regulation here?
Bad practices by NYT impact 3% of Americans. Bad practices by Amazon impact 48% of Americans.
You can be cynical and say that going after Amazon is political because more voters are impacted, but at the end of the day it seems reasonable to go after the biggest target where the biggest impact can be made to benefit Americans.