What were you expecting?
It crashes the browser by writing thousands of characters in the address bar every second, exhausting memory.
The attack is just four lines of code, and can cause an iPhone or Android phone to crash both Safari or Chrome, or reboot the entire phone itself. It even works against some desktop browsers, depending on how much RAM and CPU the machine has available.
People are sending the link around on social media disguised by a short URL, to trick others into opening it and cause them to be unable to open their browsers until a reboot is completed.