Longer lasting, sure. Less-than-lethal (or otherwise less harmful), not necessarily. Whether the host dies a few weeks after contracting the virus is not really relevant for transmissibility.

Actually, several viruses have evolved to become deadlier:

https://apnews.com/article/fact-checking-011488089270

https://www.usatoday.com/story/news/factcheck/2021/07/14/fac...

https://translate.google.com/translate?sl=auto&tl=en&u=https...