Hebrew pretty much came back from the dead and is now a thriving language.
Welsh has rebounded pretty well, too.
OTOH, it’s been tried with Irish and a lot of other languages where it just wouldn’t take. Most attempts to revive a dead or dying language don’t work.
“Welsh has rebounded pretty well, too.”
This does not surprise me. The Welsh are more stubborn, hardworking, and determined than the Irish. My grandfather was Welsh and really embodied these characteristics. He was also 1/4th Manx, but I know nothing about their traits.