A possible reason for the authors of the sm2 mod for Call of Duty ceasing their work could be a complaint from Activision

The project was based on Modern Warfare 2 (2009) but incorporated elements from several previous installments of the series. Later, the developers switched to using the engine from Modern Warfare Remastered. Originally, the plan was to release the game in a free format for anyone interested, but Activision did not approve of such a fan initiative.

The mod authors informed the players about receiving the corresponding notification and expressed gratitude for the support they had received over the past two years. So far, Activision has not made any comments on the matter.

The last video about the project was posted on the authors' YouTube channel four months ago, where they talked about the different weapons included in the mod.