"Idiomatic" doesn't mean "good". It means the normal way within the language. Personally after using both languages like Python with "truthiness" and languages that rigidly require all if clauses to evaluate to a boolean, rigidly and directly, I say the latter is unambiguously superior in practice. The former leads to surprises, sometimes even creating security vulnerabilities when a user can wedge an unexpected value into an if statement somehow.
It has unambiguously been idiomatic Python since the beginning. My opinion is that it is bad, but that's much more an opinion than the fact it has been idiomatic. And to Python's credit, part of the reason why I am so sure it's bad is precisely the experience I gained in Python using it. At the time Python was implementing the principle, I don't think the general experience of the programming language community was strong enough to know that it was a bad idea.
Python's guiding principle right now seems to be the same guiding principle as almost every other language, "let's solve as many problems as possible by adding features to the language". If a year goes by without at least one major new feature, the language must be "dead" or "failing". As the years wear on and so many languages have piled up so many features, I wonder when people will finally look around and realize that all these features, for all their superficial appeal in the small scale, are not generally helping them write better programs, or write programs they couldn't have written before, and often harm their programs on larger scales. There are exceptions. I have a hard time imagining any modern language without some concept of closures, for instance. I could name a few more; some sort of easy polymorphism (there's a few ways to get there but you need to take at least one of them... but preferably not all of them...), some sort of concurrency solution in this era, solutions for memory safety (again, multiple solutions, but you need at least one of them). But so many of these features are, in my opinion, not a net positive, their benefits far smaller than meets the eye and the costs so much greater.