why hidden robots.txt

Hello,

I discovered a strange situation on a competitor's website. They rank higher than me, but I can only access the site by searching through Google. When I try to visit it directly, a different page opens, like a cloaker. However, they've also blocked access to their robots.txt file, intentionally displaying the domain ending page design here: https://islb.eu/robots.txt Why would they do this, and what could they be hiding?

Probably to disguise what they're using the domain for. Looks like they just redirect any request that isn't featuring a Google search referrer to a fake 'this domain has expired' page. It's not just the robots.txt file eg