Why Did Albert Lasker Lock Scientific Advertising in a Safe?

David Senra says Albert Lasker locked Claude Hopkins's book Scientific Advertising in a safe for 20 years because it gave away the firm's secrets. Hopkins showed the manuscript to Lasker, founder of the firm where Hopkins worked. Lasker refused publication and told Hopkins to wait until Lasker was done making the money.

Senra calls Lasker the person who made the most money in advertising ever. He thinks Lasker later quit the agency, gave it to some employees, and left, and that only then was Hopkins allowed to publish. Senra thinks the book came out around 1920, or maybe 1930. He says it sold like 8 million or 10 million copies, almost 10 million over about 100 years, and he calls it probably the most important book ever written on advertising once you count who read it and what they built afterward.