Credit Card companies do watch for fraudulent transactions and will freeze a credit card if there is some suspicious purchase activity from the credit card.
Credit Card companies have a system in place that detects any unusual activity from the credit card and will alert the card holder about those charges and freeze the credit card until some security questions are answered.
Also some credit card companies will freeze the credit card if it's suddenly used out of the country if you don't contact the credit card company ahead of time and let them know that you'll be using the credit card in a different country while traveling.
If you do lose your credit card or get it stolen you need to contact the credit card company right away and have them freeze the account and deactivate the credit card so it cannot be used.
If you contact the credit card company and freeze the credit card soon then you won't be liable for any fraudulent charges on the credit card.
You should also sign up for credit monitoring services on your credit card so you'll be alerted more often should some suspicious activity be going on with your credit card.
Credit cards can be used even without the credit card being stolen as it's possible for some hackers to hack into websites and servers and steal the credit card information and then sell the credit card info on the dark web.