This Makkan surah was revealed in response to the proposition made by four individuals on behalf of Quraysh. After exhausting all their resources and efforts to put an end to the noble mission of Islam, their last resort was a compromise whereby both parties would unify and alternate between worshiping Allah one year and their false gods the following year. But this plan would never succeed for obvious reasons.
The prophet knew without a shadow of a doubt that at the core of Islam is the fact that worship, the meaning of which includes obedience, love, trust, sincerity and submission, is to Allah alone. Furthermore, the gift of al kawthar in the previous surah was a reminder for him to not compromise his mission for any worldly gain. Also, surat-ul-kawthar concluded by telling him that his enemies were the ones cut off (nothing good will come out of their plots and plans), thus preparing him to reject their ideas.
Notice the Arabic word used for disbelievers in this surah is al kaafiruun which is different from allatheena kafaruu (those that have disbelieved). Al kaafiruun are disbelievers that will never believe.