I want to know the answer to the following question:
What are the main reasons the conduit lines were converted to overhead  wire system?
All the background I'm provided with is that "A similar system of changeover from conduit to overhead wire was also used on the London tramways, notably on the southern side; a typical changeover point was at Norwood, where the conduit snaked sideways from between the running rails, to provide a park for detached shoes or ploughs.". Is that enough to answer the question?
Answer: no