Why nokia 3310 is so powerful?

It’s not.

That is all.

Battery that lasts for a week, incredible durability and simple design.

Memes aside, the 3310 is a very tough phone. Friend of my dad had one and to prove how tough these phones are he threw it at a wall. He was drunk that evening.
The battery and rear panel immediately came off. But put the three pieces back together and the phone works.

That same friend also dropped his phone in a pot of boiling soup. After taking the phone out, leaving it to dry - it still worked.

It's iconic and was very popular. Wouldn't call it powerful though. The design happened to be particularly durable.

Good for something that is very old.

Because it's simple. The more simple the design the more durable it can theoretically be with the right materials.