It is a microcosm, a bit of a litmus test, and an ideological battlefield of the embattled sides. But this example specifically is also a kind of infighting, of the more anarcho-libertarian tech camp that enjoys highlighting and dripping with self-righteousness about any tech related failure of government, i.e., or at least government that does not align with their ideology or control over it.
This fault line of America runs right through things like BART like an effigy or idol that America performs a kind of ritual form of battle on as proxies for all out civil war. Think of tribes you may have seen videos of where they do all kinds of elaborate dances and blustering displays and fake charges to demonstrate their power.
The glee about this outage happening to BART is very much because the libertarian tech progressive types are amused and validated by it, where something more like rashes of violent attacks on BART riders by menaces to society might be something that the "heartland" may become gleeful about, as evidence for how the ideology of SF is messed up. In the cases of violent attacks on BART riders, another camp/tribe would come out and demonstrate their fierceness; the "socially liberal" types from all over the country and even world, would rush to the defense of their ideological idols with a bewildering storm of rationalization, delusion, and excuse making for violent attackers and in defense of their ideology/cult.
It's just elaborate war dances around an idol/ideology to demonstrate how fierce and powerful each party is. BART is just one of the idols in America around which these displays of simulated conflicts happen.