Moved to Help.
First of all, try to turn OFF “Strict line breaks” in the “Editor” settings. If you turn that off, Obsidian will keep single line breaks.
But this is a Markdown editor, and this is how Markdown works. So unfortunately, you’ll have to find a workaround or a plugin if you want to display more line breaks.
You can review this thread for additional ideas: How to add multi line breaks in preview mode - #7 by OlivierPS