Why is canton the English word in Cantonese?

This was not created later, but before the invention of hanyu pinyin.

Chinese Pinyin was invented in 1955- 1957.

Before that, there were other systems for Latin spelling of Chinese, such as Athena Chu, Guoyin, Roman Pinyin and Universal Pinyin.

Some words that were widely known before the invention of hanyu pinyin have been handed down and have not changed so far:

Tsinghua, Tsinghua

Lu Xun Lu Xun

Guangdong Province

There are also some slowly replaced by pinyin:

Beijing Peking has gradually become Beijing, but Beijing dog Pekingnese still uses Peking as its root word, and this has continued.