Didn't he get in trouble for contributing to sci-hub before he died?
The whole incident is written up in detail, https://swartz-report.mit.edu/ by Hal Abelson (who wrote SICP among other things). It is a well-researched document.
The report speculates to his motivations on page 31, but it seems to be unknown with any certainty.
Information may want to be free, but sometimes it takes a revolutionary to liberate it.
but also prior to that he had written the guerilla open access manifesto so it wasn't great optics to be caught doing that