1.) Jack Ryan wasn't cancelled by Amazon. The star of it, is busy, and bored of playing the role, and was only signed on for four seasons. (This is typical of a lot of in-demand actors by the way. Few want to be stuck in a role for more than a few years. A lot of television series end because the lead actors don't want to continue - and some even break their contracts. It limits their ability to play other types of roles, to direct, etc. If you are in-demand, you don't want to be stuck in one role for too long. It's why in-demand actors will only do limited theaterical runs, and often only commit to a few seasons of a television series.)
"Neil Gaiman fantasy series Good Omens is looking good to land a Season 3 renewal by Amazon and the BBC, I hear. In anticipation of the order for what will likely be the show’s last chapter, the options on the series’ main cast, led by Michael Sheen and David Tennant, have been picked up, sources said."
no subject
Why did Jack Ryan end so abruptly? Krasinski only signed on for four seasons
Per the article, Amazon could continue it with a spin-off. They've never really acknowledged that it is ending.
2. Good Omens did very well and has a third season coming.
Here's Good Omens getting a S3
"Neil Gaiman fantasy series Good Omens is looking good to land a Season 3 renewal by Amazon and the BBC, I hear. In anticipation of the order for what will likely be the show’s last chapter, the options on the series’ main cast, led by Michael Sheen and David Tennant, have been picked up, sources said."