As for the reason, Mr. Dotcom has claimed to have been a supporter lf WikiLeaks and this was probably not of signifigance, but I would overall bet 10% that his less public involvement with WikiLeaks & WikiLeaks-type activity was part of the analysis that led to him getting targeted.

May be worth to compare the usual tactics of IP owning companies to what happened to Kim. I have a feeling that it could be shown that the kind of treatment he got was not very probable for a normal piracy case, even after accounting for his eccentric behabiour.

ALSO politically he was a failure but not so much that it was not worth paying attention to him as challenger of establishment. Even those normally ignorant of related topics but active in politics may have seen him as an agent eating their votes.