Zoro was this strong the whole postTS, if you pay attention to his behaviour you can tell but I understand people closing their eyes when Zoro is on the panels...
If I was able to pick up hints Oda has been leaving, so should have others but hating a character can cause a problem and there are also the Luffy lenses which are the main problem aka measuring Zoro with Luffy as his limit...
Also, the strength that Zoro possesses has been hidden the whole time so what you are about to see will blow your minds and for haters, it will require lots of the finest copium. Nobody is ready for Zoro's arc, it is simply glorious and I am looking forward to its magnificent ending which will give us the new sword god.