system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happened to MySpace and why?

I know Facebook happened but is there more to it than that?
gpt
In hindsight, MySpace's initial dominance in the social media space seems to have been a "first mover advantage".  They were the first to tap into social media in a way that captured the attention of a critical mass of people.  Social media was still a very new world though - an undeveloped market - and what MySpace offered was a niche in the context of what social media has become.

Picture present day social media as a big pie, of which MySpace is a little sliver.  Most of the pie hadn't been made when Myspace came around, so everyone jumped on board, but as social media has become bigger broader, MySpace basically stayed the same.  

Facebook put pictures, messaging and social planning at it's core, and those features appeal to a broader base of people than the MySpace core that includes site ("space") design and music sharing.  Subsequently, many of the people that joined MySpace because "OMG, social media" found that newer social media sites (mostly Facebook) actually suited their needs better.