one possible explanation could be that without a constant crusade for simplicity we'd be in a far worse place; the "permanent revolution" explanation.

I think the explanation is similar, but slightly more complex, than this.

I don't think we'd necessarily be in a worse place without crusades like this, because I don't really believe they have any impact on general trends in software. But that's not the same as having no impact or value.

Rather, I think these crusades are important for their niche influence; without them, we would only have the overcomplicated mainstream, without the minority of simpler options, that will never come to dominance but, hopefully, with the help of advocacy like this, will continue to have some small following.

there needs to be a constant struggle not to over-complicate, but it should be done with the understanding that over-simplification is just as problematic

While I agree with the sentiment, the latter seems to be less of a problem in practice, no?