Maybe it uploaded all the minds it was programmed to help, and then ran them all on a series of small, incredibly efficient computers, only sending duplicates across space for the security of redundancy.
A few hundred parallel copies around as many stars would be pretty darn safe, and they wouldn't have any noticeable effect on the environment. We could have one around our sun right now without noticing.
And maybe the potential for outside destruction is better met by stealth than by salient power.
If it doesn't favor just making more people to have around, why should it ever go on beyond that?
For a moment lets assume there is some alien intelligent life on our galaxy which is older than us and that it have succeeded in creating super-intelligent self-modifying AI.
Then what set of values and/or goals it is plausible for it to have, given our current observations (I.e. that there is no evidence of it`s existence)?
Some examples:
It values non-interference with nature (some kind of hippie AI)
It values camouflage/stealth for it own defense/security purposes.
It just cares about exterminating their creators and nothing else.
Other thoughts?