Norman told the club he was innocent, hence why the club put out a statement saying they'd support him until his day in court, and innocent until proven otherwise. I don't think they knew the guilty plea was coming..
Corey, god bless his naivete, thought that one of the bros putting his hand up and saying the pingers were his would get him off. Unfortunately, his lawyer soon gave him a very quick education on how drug possession laws work, and so he took the easy way out and pleaded guilty.
He could have pleaded not guilty and sought an adjournment, calling witnesses such as James Segeyaro, a UK Super League player who cannot really appear until October or so. So he could have easily put this aside until the off season. But that would mean that whatever the suspension he's getting, would have been served next season. Which would reduce his value either to Parra of some other club quite a bit. So his management advised him to plead guilty and cop the suspension this year, when Parra have next to no chance of making the finals.
Makes perfect sense.