When caps leak bad enough, particularly on a 1G, the leakage tends to take out the voltage regulation circuit. When this happens, a number of critical components are subjected to much higher voltages than they were designed to tolerate. The picture below shows what this looks like.

This type of damage can only be repaired by replacing every single blown component on the board. The problem is that it's not always so obvious which components are blown. So many times, the ECU is simply not repairable.