This is from Legal Zoom.com
A patent indicates that the inventor (or patent owner) now has the right to make, use, import, sell, and offer for sale the invention for up to 20 years (the length of time that the patent is valid). Inventors should be aware that the patent itself won't generate an income for the inventor, but licensing or selling the patent rights to another person or company willREVO sold the RIGHTS. Of course, whether it's a new product or a new technology, there's no guarantee that an inventor will get rich off of the invention.
Selling a patent outright can generate a lump sum of money for an inventorREVO did not sell the patent, but the downside is that by selling the patent, the rights to any future income are transferred to the new owner of the patent. This is why they only sold the rights Inventors must also consider the timing and the type of product. Say the patent is for a new technology, but it hasn't caught on yet. By selling the patent later, once the technology gets established and is at least moderately successful, the inventor can sell the patent for more money than when it was first issued.
It appears your difficulty comes from not understanding the language. They only sold the rights, not the patent. Simple as that.