It probably wasn’t random. You probably are very good with the account.
Things banks look at:
Do you use the card? If a card sits in a drawer with no balance, most likely they’ll close it. It’s not worth them keeping it.
How often do you pay it off? There is an algorithm that looks at your balances and how many times your cumulative payments pay the balance off. It doesn’t matter if you always carry a balance or not. Surprisingly most banks don’t like people that charge the card up to the limit and then make minimum payments and never use the card again. They like members that use the card.