If anyone is curious about Beethoven's life, I can recommend and excellent and relatively recently published biography: 'Beethoven: Anguish and Triumph', by Jan Swafford.

We see figures like Beethoven and Goethe as geniuses themselves, but the 18th century conception of 'genius' was not of a person, but of a sort of holy spirit that blessed an individual with great abilities, while remaining separate from that person.

So prior to Romantics of the 19th century taking hold of the concept of genius and re-purposing it into the one we're familiar with today, one would not speak of someone being a genius, but being graced with genius. Genius was not who they were, but something external to them that they possessed.

It's a subtle but interesting difference.