Nikola Tesla invented or contributed to: alternating current, radio technology, X-ray imaging, remote control, the rotating magnetic field, and fluorescent lighting. He held over 300 patents. He literally shaped the modern world. He died alone in a hotel room in New York City, deeply in debt, feeding pigeons.
Tesla was a catastrophically bad businessman. He tore up a contract with George Westinghouse that would have made him one of the richest people in history — reportedly worth over $300 million in today's money — because Westinghouse said the royalties were too expensive. He trusted people he shouldn't have trusted. He spent money he didn't have on experiments that didn't work. He was swindled out of credit for his inventions by people who were better at the business side, most notably Thomas Edison, who was a worse scientist but a much better self-promoter.
In his later years, Tesla became obsessed with pigeons, particularly one white pigeon that he claimed to love "as a man loves a woman." He spent his dwindling funds on pigeon care. He walked to parks to feed them. He took injured pigeons back to his hotel room to nurse them. This is either very sad or very beautiful depending on your perspective, and it's definitely not the kind of detail they include in the motivational posters.
You can be the most brilliant person in the room and still lose to someone who's better at marketing. Talent is not rewarded. Visible talent is rewarded. Tesla's genius was undeniable, but genius without self-promotion is just a hobby that happens to change the world. The world changed, and Tesla got a hotel room and a pigeon.