I think it's good idea to perceive verbs with "по" and without "по" like different verbs. Don't try to perceive them like forms of one verb for different tenses (conception of verb teens works in english, but it doesn't work in russian).

понравился says ' I began the process of liking...', and has nothing to say about whether that liking continued or not.
Ok, lets recall the english verb "impress".
If I say: "It impressed me" or "It has impressed me", what can you say about whether this emotion continued or not? The verb "понравился" works same. Both verbs focus us on bright moment in past, when we were feeling something, but both don't describe our state after this moment.

I think it's not hard to come up with sentences were "поработал" and "работал" sound almost same like "понравился" и "нравился".