I had assumed FB bought Giphy in part because Google bought Tenor. It's interesting that the FB acquisition has seen more antitrust scrutiny relative to the Google acquisition.
Didn't _Alphabet_ buy Tenor (not Google)? It seems pedantic but it's probably the over-arching corporate structure that determines the distinction here.
Edit: Actually I kind of walk this back. I don't think Tenor has ever stopped providing the same service in an open manner (i.e. via their API), which would be needed to make the argument that there is a competition concern somehow.
In the realm of social media, FB is much more dominant.
Companies that are more dominant, almost by definition deserve more anti-trust scrutiny.
The closer a company is to being a monopoly, in that specific market, the more that anti-monopoly laws will come in to play.