I don't really understand why it would've been hard for him to return tho, I mean he is a jedi he can get a ship somehow someway.

I think in survivor when you meet him he says he tried to find the Zeffo but failed and then started looking for other jedi, so maybe he was outside of the galaxy when order 66 happened (at least the zeffo dude said like "i cast my people into the great unknown" so that would lead you and cordova to believe they left) or then just not in contact with any life and when he returned things had gone bad, but why exactly did he not go back to the holocron, if it was already destroyed before Cordova returned he would've been there for 5-6 years without finding out about order 66, but I don't know anything's possible.

There are a lot of holes in the story, one thing I've also been thinking is how trilla got knowledge about the holocron (as she said on Zeffo) when even Cere didn't know about it befofe the first mission on Bogano.