Well couldn't you say the same for Gaelic Irish/Scots? Just askin'.. honestly don't know if they're exactly comparable situations.
Indeed, the situation is comparable, somehow, with Gaels. But the main difference is that Welsh is still a living language that resisted linguistic integration very well, even today, while on the other hand Gaelic has declined tremendously.
But the truth is that Gaels (whether from Ireland or Scotland) were oppressed and even ethnocided far more brutally than their Welsh cousins, hence the result.
"A man who only drinks water has a secret to hide from his fellow-men" -Baudelaire