What do you mean motivation?
Not only myself, but a lot of people find it strange for people to invest their energy and time and attention to be using a shared account to be reposting stuff hourly if not for karma-farming. And it seems to be doing this straight for days at a time, just based on the recent account history.
If that was me, I'd probably do different things instead of finding entertainment in doing the same thing again and again every hour of posting on Hacker News.