Twitter is a lightweight microblogging platform that although launched post Facebook, managed to dominate microblogging when Facebook was focused more on relationships.
My guess as the origins are that instant messenger tools like AOL Messenger, Skype and MSN Messenger were very popular. One habit people started to get into, was to set their status to something like a micro-news broadcast. Instead of messaging their friends about the innocuous news that they were setting their status about, they would just set the status to " headed out for for salsa class", " painting the living room", " back on the job market", as a way to inform people who might pay attention to us, but whom we are not sure will be interested in this tidbit of personal news or not. This type of status publication was also core to Facebook's purpose, and in some ways Facebook should have been more successful, as those news tidbits or posts would get broadcast to the person's ever growing network of friends from high school, coworkers, friends' friends, hobby friends and so on.
So why did Twitter dominate here instead of facebook? Even to this day, people get confused about audiences when posting to Facebook. Most people just have it set to friends by default and don't give it much thought. 12 years ago, this was more the case, where it didn't even occur to people to make public posts on Facebook. Twitter was just the obvious destination for public microblogging, and it was that simple. This led to making Twitter a central place for public discourse, ideation, and sentiment gathering.
There was a considerable effort to kill Twitter, with many people tweeting about leaving the platform and updating their profiles with their Mastodon links. Personally I have noticed myself getting followed by young attractive females with no followers, and so I don't believe that Elon Musk has been successful in removing Bots or spam accounts from the platform yet. However, I do support his efforts overall, and hope that it can be a platform of real consequence going forward, much less swayable by politics compared with other platforms.
I would hardly say that I am a heavy user, although recent discussions on artificial intelligence have motivated me to buy Twitter Blue, so that my posts might get some attention. One Post in particular I am hoping we'll get some traction is this one on the Is AGI the solution to Fermi Paradox?