Darren would only have studied everything casually and would have tried out various things to test if it was all real.
Sometimes, when testing them out, innocents were harmed unless he chose to target people he hated or locations where he expected them to be.
The main success that he was supposed to have was in his method of creating and using Spirit luring talismans and inscriptions.
The problem with them was that they attracted Spirits and caused them to behave aggressively no matter whether they were Spirits or Evil Spirits.
Before he realized that his actions had been effective, it was already too late to reverse them, partly out of a need for revenge and partly due to ignorance.
Ash's intervention made him believe that something was quite real about it all and that he should work harder to understand it.
That caused him to study everything more intensely before finally making a clearer decision about his future path.
