Central to being a genius is to also be ahead of your time and this means that your work is often unappreciated in your own lifetime as a result.
There are many examples of great composers who went through life largely unnoticed and achieved only mediocre results.
We must remember that in those times the concept of record sales or even recurring royalties from publishing rights simply had not been conceived of yet.
You composed a piece of music, sold it outright to a publisher and that was that.
This is one of the reasons why it was so hard to make a living as a composer, it simply did not bring in much income.
Many of the great composers made extra income through giving private lessons or performance and often through the patronage of wealthier public figures who had enough wherewithal to recognize the importance of their talent.
Aside from the fact that most composers found it financially very difficult to survive, composition itself is hard work.
It's something which must be done often and even though a composer may be a genius, expressing oneself with pure sincerity in any art form is quite a feat, unless your Mozart of course - he's the exception! The lives of the great classical composers make often make for some interesting reading especially in the cases of Beethoven, Delius and Debussy to name just a few.
It's easy to listen to their music and have a overtly romantic view of them but in truth their lives were anything but easy at all.