To call De Forest's audion (now known as a triode) an "improvement" of the diode might be technically true, but misleading: being able to amplify signals was a quantum leap in technological capability, and a necessary precursor to there being an electronics industry.

De Forest himself, however, apparently did not understand how his audion worked, at least at first, and felt it necessary for it to contain some gas. There's an excellent short biography that I will post a link to if I can find it...

Edit: This is not the article I had in mind, but it shows that initially, De Forest's audion did not have a connection to the grid, and also that De Forest was unaware that the triode arrangement could be used to amplify, and considered it only an improved diode; it was Amstrong who discovered its amplification. IIRC (from the other article I have in mind) De Forest was able to appropriate the fruits of this seminal discovery by use of his audion patents (Armstrong was later screwed over by Sarnoff and committed suicide.)

https://history-computer.com/the-audion-history-of-the-audio...