On Bybit, cross margin is the default. Most people are using it without ever having chosen it.
Same account, same trade, one setting different, nothing else open.
$5,000 account, $1,000 as margin, 10x, a $10,000 position.
Isolated: liquidated at 10%. You lose $1,000, you keep $4,000.
Cross: liquidated at 50%. You lose $5,000, you keep nothing.
Cross gives you five times more room to be wrong and charges your whole account for it. It is the right setting on a hedged book. Isolated caps the damage and pays for it by closing you out of trades that were going to work.
Neither one is the safe setting. Isolated costs you a position. Cross costs you the account.
Cross does not kill you faster. It kills you deeper.
Next in the leverage series.