Comic strip submission deadlines are usually weeks in advance of their publication date. He may have not consulted a calendar. If his life doesn't revolve around religious holidays (and it most likely doesn't), he might not have been aware that that strip's publication date was going to fall on a religious holiday. I don't see any overt signs in the strip that it was knowingly intended to be an "Easter" strip -- no colored eggs or chocolate bunnies, for example, which even non-Christians tend to indulge in on Easter.
Just like Mirimax-Disney was unaware that their antiCatholic art film "Priest" was originally slated to be released on Good Friday some years back?
You give them too much good faith and credit.