Yes, darn lucky you didn't have a fire. Great job in how you were able to fix it!
In cases like this where you have a bunch of receptacles out and it's not a tripped GFCI or breaker, it is almost always a bad connection somewhere - either in a wiring device or a junction box. You have to be persistent and methodical in pinpointing the problem.
You had an arcing fault as opposed to a fault to ground. Nowadays in houses, Code requires an arc fault breaker for bedroom receptacles. I wonder if they should be using them in RVs?
Wire connectors (aka "nuts") do not have to have the wires pretwisted, but this is the normal practice in the commercial/industrial sector. Otherwise, there is a bit of a knack to holding the wires together and twisting the connector on to get the wires to twist properly. Once the nut is twisted on properly, there ain't no way the wires will come apart. You can remove one to test if you have it right. Gets much more difficult when you have 4 or more wires, in which case, it is just better to pre-twist them anyway and trim them. The yellow connectors in your coach have wings on them to make the twisting process easier. I like these better but they do take up more room in a box. There is a little plastic tool that you can use for the wingless ones.
In all my decades of being in the electrical business, I have to say that I have never, ever heard of taping wire connectors. It's overkill but perhaps an extra good measure in an RV that shakes, and moves - unlike a building. Good idea to install the plastic connectors on the box with 2 cables each. I'm not so sure that 4 cables in the original metal connector was okay by NEC?
FWIW, I thought I would just say that there is absolutely nothing wrong with the design of 120V receptacles in RVs. They are what is used in manufactured homes also. The problem is when whoever is doing the install does NOT terminate the wires properly. Can be done with a screwdriver (if done slowly and carefully), but there is a correct/proper tool for punching down the wires and I would expect factory workers doing these to have the proper tool but it sounds like maybe not out there...
If you had spare time some day, it might be an interesting excercise to pull off a few receptacles and check the connections. In one I removed in our TT (to relocate up 6" for a cab. mod.) I found one conductor was improperly terminated. There are 2 "stabs" for each conductor and on one of them, only one stab had a wire connected and the other was all bent to crap and the wire unconnected. I doubt that the proper tool was used. I am going to check all the others.
Gil & Deb & Dougal the Springer Spaniel