In addition to what @user6591 wrote about Kayin wanting to take Hevel's twin sister, the Pirkei DeRabbi Eliezer 21:7 elaborates and writes:
Rabbi Zadok said: A great hatred entered Cain's heart against his brother Abel, because his offering had been accepted. Not only (on this account), but also because Abel's twin-sister was the most beautiful of women, and he desired her in his heart. Moreover he said: I will slay Abel my brother, and I will take his twin-sister from him, as it is said, "And it came to pass when they were in the field" (Gen. 4:8). "In the field" means woman, who is compared to a field. (Sefaria translation)
So we see that he was jealous not only of Hevel's sacrifice gaining acceptance but also because he was jealous of him for marrying his sister whom he coveted.
The Targum Yonasan, Bereishis 4:8 provides a clearer reasoning on what this jealousy about Hevel's sacrifice gaining acceptance was predicated on:
And Cain said to Abel his brother, Come, and let us two go forth into the field. And it was that when they two had gone forth into the field, Cain answered and said to Abel, I perceive that the world was created in goodness, but it is not governed (or conducted) according to the fruit of good works, for there is respect to persons in judgment; therefore it is that thy offering was accepted, and mine not accepted with good will. Abel answered and said to Cain, In goodness was the world created, and according to the fruit of good works is it governed; and there is no respect of persons in judgment; but because the fruits of my works were better than thine, my oblation, before thine, hath been accepted with good will. Cain answered and said to Abel, There is neither judgment nor Judge, nor another world; nor will good reward be given to the righteous, nor vengeance be taken of the wicked. And Abel answered and said to Cain, There is a judgment, and there is a Judge; and there is another world, and a good reward given to the righteous, and vengeance taken of the wicked. And because of these words they had contention upon the face of the field; and Cain arose against Abel his brother, and drove a stone into his forehead, and killed him. (Sefaria translation my emphasis)
So it would seem that the heart of this jealousy was based on a deeper more profound (albeit incorrect) outlook of the running of the world. Kayin saw Hevel's 'winning' sacrifice as an example of Divine favouritism which he wasn't able to 'get over'. It was this intense jealousy that drove him to lash out so violently.