I'd like to see your source for that claim. At first glance it seems that popularity of Camino, both among its developers and its users, has been declining for years.
A big counter-example is Opera Software switching away from their own engine to WebKit/Blink.
Opera has a paid staff of full-time engineers, which makes rewriting a browser on top of a new engine a lot more feasible.
You're right in that if Camino had the developer time it had in its heyday it might have made the jump and survived, but the end of Gecko embedding is what made it impossible for Camino to continue to be maintained indefinitely by one or two people.
A big counter-example is Opera Software switching away from their own engine to WebKit/Blink.