Google's new logo was created by Russian designer in 2008
dailytech.com
dailytech.com
Incidentally the Tokyo 2020 olympic committee is in the late stages of a similar furore over their logo, a stylized "T" with some some adornments, which turned out look similar to the logo of a Belgian theater company:
https://www.google.com/search?tbm=isch&q=tokyo+olympics+thea...
Equally silly in my opinion, but people then found more blatant examples of copying in the designer's past work so they wound up scrapping the emblem.
I would certainly argue with "inarguably".
Kortunov created a really good icon design, but it's not hard to imagine other people independently coming up with something similar.
http://freshtutorial.com/wp-content/uploads/2011/09/Big-Goog...
http://takedesigns.com/wp-content/uploads/2013/02/free-2.png
http://designurge.com/wp-content/uploads/2013/09/g__by_mauxw...
I think it's just a case of parallel evolution. Mix up a blend of influences like Google's existing primary color-based design, Microsoft's Windows Logo, Google Chrome logo, and some aesthetic sense, and you'll get a lot of logo designs that look similar.
This article is interesting, but it has a terrible title and overly-confident conclusion, which is not supported by the evidence
(And, maybe this is interesting. Someone independently derived a Kortunov-style logo from the new Google version. So there is a discussion among designers comparing the two logos: https://dribbble.com/shots/2224596-Google-redesigned-G-lette... )