The fact that the 2 arrested individuals are teenagers is all you need to know about the complexity of the attack on Talk Talk.

This was a script kiddy attack, no more no less, a lot of people claimed responsibility from ISIS to chancers requesting ransoms but ultimately this was due to talk talk having incredibly poor security. That they have recently been hacked a few times just confirms that they are a soft target with lots of customers data.

The fact these kids are kids is not the defining reason this was a simple attack, there are some smart kids out there, but I imagine anyone with some decent skills would have obfuscated their tracks enough to not get caught. These are the LHF of hacks.