Why are Hindu-Arabic numerals connected to Devanagari?

The connection between Hindu-Arabic numerals and Devanagari lies in their shared origin in ancient India. The Hindu-Arabic numerals originated in India during the 6th or 7th century, and these numeral forms were subsequently adopted into the Devanagari script.12

While the numerals used in the West are commonly called Arabic, they are more accurately termed Hindu-Arabic because they were developed in India and later introduced to Europe through the work of Middle Eastern mathematicians. Devanagari, which is the script used to write Hindi and other languages, maintains its own set of numeral symbols that reflect this historical development. Today, while the constitution of India provides for the use of international (Western) Arabic numerals, the traditional Devanagari numerals remain a part of the script's broader system.132