6C3 Why is H3PO3 stronger than H3PO4

[Gabrielle Arreglo 3F]

The textbook says H3PO3 has a pKa of 2.00 whereas H3PO4 has a pKa 2.12, meaning that H3PO3 is stronger because it has a lower pKa. However, how does this fit in with trends of acid strength? Because H3PO4 has more oxygen atoms and is more electronegative, shouldn't it be more willing to accept an electron and result in a stronger acid strength and lower pKa)?

[Amal Aboumerhi 3E]

Hi! H3PO3 is more polar, so the OH bonds will be weaker, making the H+ easier to lose, and causing H3PO3 to be more acidic than H3PO4.