There used to be intent to the act of using a computer or going online

Nowadays we have access to the Internet and a computer at all times on our person

There was novelty and satisfaction with just being able to use it.

And as for the graph, well as it relates to the topic at hand:

And with the rise of social media and people always showing their best online you have people comparing themselves to those people who always show the good but never the bad parts of their lives. So people think they're doing terrible when infact their just doing normal.

And with the spread of negative emotion enforcing information online (which spreads via algorithms looking for what gets the most reaction and pushing it further (this is a whole topic unto itself)) you end up with a lot of people only seeing the bad in the world.

Not to mention the constant drip feed of dopamine from our little windows into the infinite. (Screaming righteous anger into a comment section, seeing funny memes, watching your favorite influencers do great in life)

You end up with a perfect storm of shit leading to a terrible feedback loop and people being unable to cope (and likely not learning healthy coping skills). Though it's not the only reason for it (as we can never truly know the mind of another or why they would do such a thing (I've torn myself up on that topic of for years about people I've cared about)) it sure as shit ain't helping.