[yyyk]

DisplayPort is royalty-free while HDMI charges licensing per unit. Additionally, Intel strongly supported DP so many boards came with support even if there was nothing to connect it to, and Intel ensured support in USB specs. Eventually enough display manufacturers added support* and DP became common enough, this generated demand and we ended with a self-reinforcing system. There's still a lot of HDMI, so I wouldn't say the computer world is standardized. In my experience, people just use whatever port is available...

* Display turnaround time is significant. Displays can survive a decade comfortably. A few people brag about their 10000K display with 10000Hz refresh rates, but many people just keep their display until it drops or until they buy a new system. So DP took a long time to be universally supported and that hampered adoption for a long time.