There is no "95 years after publication" rule in the EU, so you cannot say the Sonny Bono act was a "harmonization".
Wikipedia also states (with some sources), that "Since 1990, The Walt Disney Company had lobbied for copyright extension." It was in their best interest, they had the money, so no surprises there. I'm sure they weren't the only ones, but the largest, for sure.
True, although in this case the US law is perhaps better than the EU one; the EU lacks any exceptions for works of joint authorship, including works for hire, so it's 70 years from the death of the last surviving author, which would usually exceed 95 years.
Wikipedia also states (with some sources), that "Since 1990, The Walt Disney Company had lobbied for copyright extension." It was in their best interest, they had the money, so no surprises there. I'm sure they weren't the only ones, but the largest, for sure.