Here's another explanation that's pretty good reading.

https://www.thegospelcoalition.org/blogs/kevin-deyoung/who-are-the-144000-in-revelation/

Here's the first explanation I found that made sense:  https://davidjeremiah.blog/the-144000-in-the-book-of-revelation/

I used to be almost afraid to read the book of Revelation, but now I find it one of the most interesting books of the bible.  I also used to feel a bit afraid of the largest book in the bible, Isaiah. One of my favorite books is of course Psalms and also the book of Daniel.  Lots of comfort in those two books.

This link has a really good vid (3 1/2 minutes) and you might learn more than you want to know!

https://www.gotquestions.org/144000.html