The whole point of patents is to allow inventors to keep control of their invention for a limited time after which others can freely use their inventions without any restrictions.
Patents are not intended to protect inventors, but to foster innovation by encouraging inventors to publish their methods instead of trying to keep them secret.
https://en.wikipedia.org/wiki/Patent is good reading.
Copyright was originally limited in the same way, but the copyright term has been extended so often to make this kinda meaningless. This is called the “Mickey Mouse” effect; https://www.washingtonpost.com/news/the-switch/wp/2013/10/25/15-years-ago-congress-kept-mickey-mouse-out-of-the-public-domain-will-they-do-it-again/?utm_term=.fbf445adcbca