He is not a citizen of El Salvador, he is Venezuelan. The sole reason he was classed as a member of that criminal organisation are his crown tattoos, and 'secret inside information'.

The Guardian article gives some more background, and explains these (catholic) tattoos:

https://www.theguardian.com/us-news/2025/apr/01/its-a-tradit...

(Hint: there are legitimate reasons for receiving asylum in the US as well.)