If they blatantly ripped off the design and called it something like Creddit

Again, reddit doesn't own any patents or trademarks that would allow them to successfully sue. Would you be surprised to learn that reddit themselves ripped off another site's design?

Back before reddit there was digg. Reddit grew massively once digg went downhill. Look at this screenshot of what digg used to look like. Does that site layout look familiar?

Also, reddit clones have been around for years. Voat is a popular one that users from a few years back will remember. They closed down, but not because reddit made them. There's also sites like saidit.net that are actual reddit ripoffs that are still up (albeit with a MUCH smaller userbase).

If Apollo branched out and reddit sued them for ripping off their content, this means that digg could have sued reddit a looooong time ago, and that never happened because it would've been frivolous at best.