We have already had 3 guys just in the last 5 or so years alone who have won 3 slams in one year along with all those masters titles. Prior to that, you had less do it in 40 plus years. Who was it? Wilander? And before that only Laver managed such?
Conveniently ignored here is the fact that prior to roughly the mid-1980s the Australian Open was usually not on the schedule of the top players, thereby drastically reducing the chances of scoring three in a year.