This is no arbitrary sentence. The fault was all along their own. The fruit of their own ways is death.
Related Commentaries of Proverbs 1:29
Proverbs 1:29-31
29 For that they hated knowledge, and did not choose the fear of the LORD:
30 They would none of my counsel: they despised all my reproof.
31 Therefore shall they eat of the fruit of their own way, and be filled with their own devices.