The Wikipedia article goes on to talk about G+'s very low engagement. I wouldn't be surprised if Twitter's engagement rates were somewhere near Facebook's.

> User engagement on Google+ was low compared with its competitors; ComScore estimated that users averaged just 3.3 minutes on the site in January 2012, versus 7.5 hours for Facebook.[22][23]

(https://en.wikipedia.org/wiki/Google%2B#Growth)

That makes you question if they actually had 300 millions "active" users.

High MAUs doesn't necessarily translate to high DAUs.

Indeed, and high DAUs doesn't translate to a high number of engaged users either. Just a 301 HTTP redirect through a domain as part of a chain can count as DAU and mean nothing.

yeah i visited g+ primarily for the active dev communities oriented around google products. def just once or twice a week and the activity on those "circles" was pretty slow

Slow growth/lack of user traction was what caused Google to pull the plug. Its a similar overarching problem to Twitter, but more of users being disinterested than actively repulsed due to the content the most popular users of said service post...