Mandarin or this kind of standardized written Chinese was formalized by a National Commission and chosen during the Republic of China era, this is the document from 1932 now digitally stored in the archives of Taiwan, see: https://taiwanebook.ncl.edu.tw/zh-tw/book/NCCULIB-9900012902...
Even without the CCP, Mandarin would have become the national dialect and dominated Chinese speech, etc. The CCP merely continued on the work because it was so useful and the easiest route to go as there had been so much work done and a system put in place by the previous regime.
^this link loaded better, its the same document, seems to be from Georgia Tech.
For non-Chinese readers, the document says that the dialect from Beiping (aka Beijing) should be adopted as the standard and then lists rules on pronunciation, how to pronunce using a Latin-based script, etc.
Even without the CCP, Mandarin would have become the national dialect and dominated Chinese speech, etc. The CCP merely continued on the work because it was so useful and the easiest route to go as there had been so much work done and a system put in place by the previous regime.
EDIT: https://cpb-us-w2.wpmucdn.com/sites.gatech.edu/dist/d/987/fi...
^this link loaded better, its the same document, seems to be from Georgia Tech.
For non-Chinese readers, the document says that the dialect from Beiping (aka Beijing) should be adopted as the standard and then lists rules on pronunciation, how to pronunce using a Latin-based script, etc.