YouTube Data API gets channel info for some usernames but not for others

Question

I am trying to get snippet,contentDetails,statistics part string by using YouTube Data API v3.

When I fill in forUsername field with GoogleDevelopers it gets the details.

But when I fill in the usernames (custom_urls) for other channels say InfinityLearnNEET, it fetches 0 results.

I tried for the following urls:

https://www.youtube.com/@InfinityLearnNEET
https://www.youtube.com/@itsreallycrazy
https://www.youtube.com/@Mrcrazyvamshi

I wonder why?