The New Culture Movement of the Republic of China advocated vernacular Chinese.
This is largely a political consideration.
Because the words used in writing articles in ancient times were different, it led to two language forms: vernacular and classical Chinese. Ordinary people can't read books and learn effective knowledge. In order to expose more people to new cultures and ideas, Hu Shi and others advocated the spread of new ideas in vernacular Chinese. Let more people participate in the reform in China.
The main purpose of studying classical Chinese now is to let the things left by our ancestors be passed down, so that no one will read precious documents such as hundred schools of thought in the pre-Qin period or the twenty-four histories in the future.