Chandra, the Moon, owns Karka, and it is the only sign the Moon owns. Surya owns one sign as well, Simha, while the other five grahas own two apiece. That asymmetry is structural in jyotisha and it makes Karka and Simha the two signs whose lordship cannot be shared or diluted.
Guru, Jupiter, is exalted in Karka, with the fifth degree given as the exact point. Mangala, Mars, is debilitated in the same sign, with the low point at the twenty eighth degree. The two sit near the opposite ends of the sign, which means the beginning and the end of Karka carry very different weight, and a reading that treats the sign as a uniform block will miss it. Jupiter exalted in the Moon's own sign is among the more favourably regarded placements in the system, and the classical texts return to it repeatedly.
The nakshatras crossing Karka are the last quarter of Punarvasu, then Pushya entire, then Ashlesha entire. Pushya is ruled by Shani in the vimshottari scheme and Ashlesha by Budha, and Pushya is widely regarded as among the most auspicious of the twenty seven, which sets up an unusual situation: a mansion of high standing ruled by the planet of restriction, sitting inside the Moon's own sign, in the arc where Jupiter reaches its highest dignity. Jyotisha does not resolve such convergences into a single verdict. It reads them as layers, and the layers are expected to disagree.