Luthor being prepared for things I think is very acceptable. The only thing he had was a substance that could get superman incredibly powerful by absorbing sunlight but also overload and kills him. Now how he know about invasion? he is the goddamn lex lol
Doesn't really justify him completely disapearing from the plot for more than half of the run only to show up and save the day. And that's only half of the convenient part. I mean, you gotta admit, Wraith suddenly deciding he should sacrifice himself just so that Superman wouldn't die and or/ be responsible for the death of thousands despite the fact he hated him the issue before is the very definition of convenient.
Hold those chains, Clark Kent
Bear the weight on your shoulders
Stand firm. Take the pain.