I saw no one mentioned the following and you said you were weak in doing electrical things.

When you wash an engine and it does not start, it will most likely be a wet distributor cap and wires. I know you drove home without the engine missing so the wires did well but there are pockets of water elsewhere on the engine that can come into play.

The heat of the engine boiled some lingering drops of water into a vaporous, steam, for as an example. You got it home a parked it in a garage or not it does not matter but convection took over.

Vapor rose up around and into the distributors cap. The cap does not have a waterproof seal even though Volvo does make Marine engines that are more expensive. Money overrules invoking the use of technology, even on exotic cars I will bet.

The cap never becomes as hot as the engine but nice and warm on long trips.
The cooler cap condensed the incoming vapor into water droplets.
This shorts the rotor button to the top of the cap or contacts of the wire to one another inside the cap. The paths are scrambled, delayed or shorted out to ground.

I use an 8-inch long cabinet screwdriver that fits between the cap and under the clips. Unclip the cap with wires attached and dry out the insides with a dry lint free absorbent cloth.

Pop it back on, making sure it is located down into the notch on the distributor’s body. You should not be able to slide it around with a rotation of your wrist and it sit flat. Then attach the spring clips over the lands on each side. If you are all the way down, they should snap back over as easy as they came off.

Hope that turns out to be helpful as the other possibilities are not as easy to grapple with.

Phil