All of those systems have outages all the time, mostly isolated incidents when it comes to NYSE, CME and similar (here is the outage page for NYSE for example:

All of those systems have outages all the time, mostly isolated incidents when it comes to NYSE, CME and similar (here is the outage page for NYSE for example: https://www.nyse.com/market-status/history https://www.nyse.com/market-status/history). Visa, Mastercard and others have nationwide outages from time to time too, they're in no way invincible like you seem to imply. Latest Visa outage I can remember must have been around 2018/2019 sometime, but probably it happened later than that too, except I didn't notice it then.