I think you’re underestimating how qualified some of your examples of unqualified managers were compared to Vinny now.
Eddie Howe has been a manager for 15 years, nearly 600 games and previously spent 5 straight years doing very well with Bournemouth in the PL getting linked to all the top clubs and England, he was hardly an unknown.
Potter again, 15 years experience as a manager.
Andre Villas-Boas won an invincible domestic treble in Portugal and the Europa league in his second season as a manager at 33 years old - still the youngest manager ever to win a European competition.
Zidane had been assistant for 3/4 years with the specific intention of preparing him to takeover.
Keegan was appointed midseason with Newcastle in danger of being relegated to the third tier, so not really a comparable job.