And even if you were up against a state-level actor and/or were naive enough to enable data transfer from a public charging port, malware delivered over USB certainly would not:

1. alert you to its presence by causing your phone to misbehave in such an obvious way
2. miraculously disappear when the phone is unplugged only to reappear when plugged back in
3. affect devices on different OSs in almost the exact same way

A dirty power supply, on the other hand, would do all three of these things.