Because the Day of Resurrection is a great affair and all that is great, has many qualities, and many names, such as the sword, when it became greatly placed, and they confirmed its usefulness to them, they collected 500 names for it, and there are several examples to that.
And Day of Resurrection , since it a great event, and its horrors abounded, Allah gave it many names in His book, and described it with many descriptions.
(Ref: the Great Judgment Day by Sheikh Omar Sulaiman Al-Ashkar – May Allah’s Mercy be on him)
لأن يوم القيامة شأنه عظيم وكل ما عظم شأنه تعددت صفاته، وكثرت أسماؤه، كالسيف لما عظم عندهم موضعه، وتأكد نفعه لديهم وموقعه، جمعوا له خمسمائة اسم، ولذلك عدة أمثلة
فالقيامة لما عظم أمرها، وكثرت أهوالها، سماها ﷲ تعالى في كتابه أسماء عديدة، ووصفها بأوصاف كثيرة.
(المرجع: القيامة الكبرى للشيخ عمر سليمان الأشقر-رحمه ﷲ-)