Golf distance increases are predominantly equipment/technology.
There is no question athletes today are on average physically stronger / faster than their counterparts from 100 years ago (Pineda types notwithstanding). However, I do not believe the gap is as great as you think. There is a line of MLB fireballers Johnson, Feller, Gibson, Ryan, Johnson, Verlander all throwing 100 MPH or close to it. There was never some massive leap in fastball velocity from one generation to the next. A slow increase generation to generation, sure. Nothing close to 75 MPH to 100 MPH across those 5 generations of pitchers.
Grichuk in 1920 hit 200 HRs? Give me a break.