Oxygen is always divalent while sulphur can form 2, 4 and 6 bonds because

Given data: oxidation state of sulphur and oxygen.

Formula/concept used: Stability of oxidation states for oxygen and sulphur.

Detailed explanation:

Sulphur shows variable oxidation state due to the presence of vacant d-orbital.

Electronic configuration of Oxygen $=\left[\mathrm{He}\right]2s^{2}2p^4$

Electronic configuration of Sulphur $=\left[Ne\right]3s^{2}3p^{4}3d^0$

Thus, due to the absence of vacant d-orbitals in oxygen, it is always divalent while sulphur can form 2,4 and 6 bonds.