ELI5 If ECT cures depression, why is it so common for people with epilepsy to have depression?

ECT (electro convulsive therapy) is usually a last resort to treat treatment resistant depression. It uses brief electrical currents to trigger a controlled seizure in the brain. So why is it so common for people with epilepsy, who have seizures frequently, to have depression? Stupid question, I know, sorry. I’m not educated on seizures.