It takes a long time to design and a lot of material to make a big transformer and they last for decades. They are critical infrastructure so when one fails you want it replaced or repaired quickly but they are too expensive (millions of dollars/pounds/euros) to keep a spare unit idle for decades and the lead time for a new large power transformer might be six months or even longer. So repair makes sense, especially if it can be done on site because moving a big metal box full of oil, steel, and copper that weighs hundreds of tonnes is a major logistical exercise.

This isn't something that can be done by a company that 'moves fast and breaks things' and disappears next year.