Anand has left to work at Apple. How could he hold onto ownership without everyone and their dog bringing up the obvious conflict of interest every time the site gave a good review to Apple or a bad review to one of Apple's competitors? I've already seen people complaining about it on places like Reddit.
This seems like the most plausible reason. I'm curious why he didn't sell it off before he left to work at Apple. Perhaps he didn't have the deal ready yet.
Nothing wrong with exiting. It's dangerous to start a business with the intention of never exiting.
Sometimes you just want to move on to better/bigger things.
From the story, ''AnandTech has been profitable since its inception; it’s been on a great growth curve these past couple of years and we’ve always been able to do more with less, but lately there’s been an increased investment in high quality content.''
Additionally, ''...they [Purch] have a sustainable business model, are profitable and have the sort of reach AnandTech needs to really hit the next level.''
If the business is profitable and has been from its inception, it could be possible investors have had a sizeable return on investment. If this is the case and earnings are steady, it's a large risk to transfer ownership to a new stakeholder for the sake of 'growth'. For example, new ownership and more users may alienate the existing, profitable userbase.
However some web businesses may require 'user growth' as a minimum industry requirement to stay alive.