From what I have read, there was a greatly decreased yield of grapes
because heavy rains washed away the pollen. (In 1945 the yield was
greatly reduced by frost. )There was much rain in July and then
drought in August. Then September was very sunny. The grapes were
small and had thick skins. The wines had very deep color and much
tannin. As a result, many considered the 1959s, which had a better
balance early on, to be better than the 1961s.
For whatever reason, I remember that many fine red Bordeauxs from the
50s and 60s tended to have less alcohol and needed at least 10 to 20
years of age. Some were quite concentrated in color, body, and taste
however. Things started changing in the Parker era when wine became
more drinkable at an earlier age. Perhaps the grapes were picked later
with higher sugar content. Also the amount of press wine added in the
final blend likely was reduced.