SBI and ICICI - Why are some banks more important than others?

The Reserve Bank of India has named State Bank of India, the country’s biggest public-sector bank and ICICI, the largest private sector bank as Systemically Important Banks (SIB) in India. The designation implies that SBI and ICICI are Too Big To Fail (TBTF). This means the survival of both banks is critical for the stability of the financial system and the economy as a whole.

https://in.finance.yahoo.com/news/why-banks-more-important-others-051018955.html