Answer:
made relatively little money from his invention
Step-by-step explanation:
The passage explains the invention of the computer device, mouse, by Douglas Engelbart.
We can learn from the text that the mouse was not instantly popular. Only around 20 years later it was started to be used globally with computers. By that time, Engelbart’s patent expired, meaning he did not earn any money from sales and usage of the mouse.
Because of this, as well as the line “unfortunately for Engelbart's bank account”, we can conclude that the passage tries to point out the fact that Douglas Englebart did not make much money from his invention, despite it being so widely popular today.