Putonghua is the official version of Mandarin which the Communist government determined was to be the official language of the nation. It was created in 1949 and modeled mostly but not entirely on the variety spoken in Beijing.
Although Putonghua seems to be killing off a lot of dialects or even microlanguages, I have a feeling that this is mandatory. Nevertheless the process of accelerated language change in China (Why?) seems to be even catching up with Putonghua. For instance, Putonghua of course was modeled on the Beijing language. However, this was Beijing Mandarin of 1949, and it was also the language of the suburbs, not to the city.
Since then, Putonghua has taken off on its own and so has Beijing Mandarin with the strange result that the hard Beijing Mandarin of hutongs in the center of the city is now often unintelligible to Putonghua speakers! So this is a case of a standard language and the lect it was modeled off taking off via independent evolution such that 70 years later, the original lect is no longer intelligible with the Standard that was modeled on that very lect!
Chinese lects are wildly different, and tones adds another mess into the matter. This has shown up even in Putonghua, where some Putonghua varieties are now unintelligible with the rest of Putonghua due to severe influence of the local lects on the standard and possibly regional evolution of the standard! Hence even Putonghua seems to have split off into several languages itself! Thus Guangdong Putonghua, Anhui Putonghua, Shanghai Putonghua, Jianghuai Putonghua and Zhengcao Putonghua are no longer fully intelligible to Putonghua speakers outside the region!
In addition, Taiwan Mandarin, Tibetan Mandarin and Malay Mandarin have all taken off on their own independent evolutionary tracks such that these are no longer fully intelligible to Standard speakers either! So since 1949, Putonghua has split into at least 8 different languages that lack full intelligibility with each other!
It seems the Chinese tried to lasso that wily creature called the Chinese language to rein it in and domesticate it somehow, but the wily creature keeps slipping away due to its endlessly morphing patter.