You are right about first part, [], empty array is an object and object is always truthy. Hence, if you use if([]){console.log('its true')} you will see the log.
However, special case about == (double equal) is that it will do some implicit coercion.
Since left and right side of the equality are two different types, JavaScript can't compare them directly . Hence, under the hood, JavaScript will convert them to compare. First, right side of the equality will be coerced to a number and number of true would be 1.
After that, JavaScript implementation will try to convert [] by using toPrimitive (of JavaScript implementation). Since [].valueOf is not primitive it will use toString and will get ""
Now you are comparing "" == 1 and still left and right is not same type. Hence left side will be converted again to a number and empty string will be 0.
Finally, they are of same type, you are comparing 0 === 1 which will be false.