Prior to and at the time that the King James Version of the Bible was written, "Profligate" has a completely different meaning, and it was a past participle:
A. adj.†I. As a past participle.
- Overthrown, routed. Cf. profligate verb. 1. Obsolete.
1535 T. Legh & J. Rice Let. in J. Strype Eccl. Mem. (1721) I. App.lvii. 145 The Canon laws..with their Author, are profligate out of this realm.
1548 Hall's Vnion: Henry VI f. clxviij By whiche onely pollicie, the kynges armie was profligate and dispersed.
Profligate did not take on its current meaning until after the publication:
II. Adjectival uses.
2. Given to or characterized by licentiousness; debauched.
1627 P. Hay Advt. Subj. Scotl. 71 All Prodigall and Profligate Persons, who by Ryot of Lascivious and Distemperate Lyfe, doe destroy their Patrimonie.
1647 N. Ward Simple Cobler Aggawam 39 When States are so reformed, that they conforme such as are profligate, into good civility.
When the meaning changed, the Bible did not. It was a criminal offence to change the Bible, and the people had, by then, become used to the parable of the Prodigal Son.
At the same time, "prodigal" had the required meaning:
1.a. Extravagant; recklessly wasteful of one's property or means. Also in extended use.
c1485 (▸1456) G. Hay Bk. Gouernaunce of Princis (1993) i. 61 Ffor jt is lesse maistry to be wrechit gredy and fast haldand, or to be fule large and prodigal — na to be wis liberale and large.