That’s what Fargate is.
If you're gonna use containers, use containers. If you want someone else to manage the container for you, use Lambda.
Create a simple ping/pong HTTP service in both and you'll quickly see difference in everything from billing to startup time.
If you're gonna use containers, use containers. If you want someone else to manage the container for you, use Lambda.
On the other you're saying "you can make fargate spin up a container for an event, but it would be too slow for any useful event driven computing", which is the truth, but it contradicts your initial comment.