The origin of the remarkable Curie temperature ($T_c$) enhancement in monolayer ${\mathrm{Fe}}_3{\mathrm{GaTe}}_2$ (FGaT, $T_c$ ∼ 240 K) relative to isostructural ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ (FGeT, $T_c$ ∼ 130 K) remains unresolved. Here, we employ a combined energy mapping + spin spiral approach to disentangle competing intralayer and interlayer exchange interactions in ${\mathrm{Fe}}_{3}X{\mathrm{Te}}_2$ (FXT, $X=\mathrm{Ge}$,Ga). Our results reveal that FGaT's significant $T_c$ enhancement arises from a weakened intralayer antiferromagnetic coupling within the outer ${\mathrm{Fe}}_a$ layer concurrent with a strengthened interlayer ferromagnetic coupling between ${\mathrm{Fe}}_a$ and the middle ${\mathrm{Fe}}_b$ layer. Meanwhile, we quantitatively separate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction from isotropic exchange mechanisms, revealing attenuation in both intralayer ${\mathrm{Fe}}_a\text{−}{\mathrm{Fe}}_a$ RKKY coupling and superexchange interactions. Furthermore, we identify strain as tuning knobs for improving the $T_c$ of the ${\mathrm{Fe}}_a$ sublattice, providing quantitative design principles for achieving room-temperature magnets. These findings resolve persistent questions on the origin of $T_c$ enhancement while establishing rational design strategies for novel two-dimensional magnetic materials.

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• Magnetic interactions
• Transition temperature
• 2-dimensional systems
• Thin films
• Density functional theory
• Spin wave theory