It would be extremely unlikely for all wires to simultaneously fail
It is exponentially more likely that the spark is being lost in the cap, or the coil just can't jump the gap inside there. Your coil should have zero troubles jumping 1/4 inch. And most will jump 3/8, and many will go 1/2 and some will go 3/4.
The thing is this, you can measure the voltage at the coil and find it adequate, just like you can measure your water pressure in the house, and find it adequate.
But when you turn on the tap, you might find nothing but a trickle coming out, like at the toilet; that's why it has a flush tank. And so it is with electricity, you got the pressure, but do you have the flow?
This is why my first test is always bypassing the entire electrical system, by jumpering the battery directly to the ignition system,with a 10ga wire, and then engaging the starter, usually, also with an auxiliary start switch. In this way I am guaranteed both pressure AND volume.
Consider this; your starter cable has how many strands in it? You can cut all but one strand, and still measure battery voltage. You can cut the last one too, and solder in a single strand of the thinnest wire you can find, and still measure battery voltage. But that wire will not pass enough current to crank your starter, power your coil, or light a headlight or maybe not even light your dash bulbs; even tho it reads battery voltage.
If you suspect you have this problem, pull some amps thru that blue wire and see. Hook a headlight up to it and see if it will light, and how brightly does it shine? Jumper wires are your friend,make some.
