Sorry Siegfried but making long-term generalizations about "the political class" and PMs throughout the post-war period just doesn't work. The game of politics and the position of the PM has changed greatly especially after electoral reform in 1994, administrative reform in 2001, and the rise of television as a factor in politics since the 1980s. What makes a popular/successful (or
unpopular/unsuccessful) PM today is very different from what made one during the "55 system." Some of the most successful PMs of the earlier period would probably have been failures today (e.g. Sato who hated tv cameras covering him) and also the reverse (Koizumi would never have come to power in the previous era). Such generalizations across time without taking into account how much politics in Japan has changed in the last 20-30 years is a non-starter as an explanation.

Best regards,
Ellis