The only thing I can think of is by forcing the coil to just a gap in the air versus in the combustion chamber with fuel, may have caused the rotor/distributor to arc and start making contact. It's purely a guess, but similar in concept to what can happen when there is a loose connection in a battery cable. Sometimes honking the horn at the same time you try to engage the starter will cause enough current to flow to get an arc going and maybe even some carbon tracing which will be more conductive than the other crap that forms over time on the rotor and distributor cap leads.
You could try wire brushing the rotor contact points and leads in the distributor cap to see if removing the more resistive corrosion will give you a more reliable spark. If so, then you know that starting with a new cap and rotor will not be money wasted.
-Rod