Encyclopaedia Britannica $($EB$)$ failed because:

They didn$$t understand CD$-$ROM technology.

They did not know how to manufacture CD$-$ROMs

Their business model selling print$-$based encyclopaedia$$s door$-$to$-$door could not function in a world of CD$-$ROM based encyclopaedias

CD$-$ROM based encyclopaedias were superior to the text$-$based