Y se convirtió en una prenda ….

It might have something to do with the variables for the change verbs. As you know, some verbs indicate an accidentals change and others an intentional change. Similarly other verbs indicate a change that happens quickly and others a change that happens over a longer period of time. Maybe one of these variables was relevant in the exercise.

Hola John, 

This might help-

 https://spanish.kwiziq.com/my-languages/spanish/exercises/judge/1701/4842319

Saludos

Sorry, wrong link. This is what should help:

Using convertirse en / ponerse / hacerse / quedarse to express "to become" (Spanish verbs of change)

And maybe this one...

Using Spanish verb volverse to express to become/to turn (verbs of change)

I think at times they're interchangeable. Rather nuanced at times also. I used the wrong verb hacerse. I need to memorise them better.