What makes pk2 of fumaric acid smaller than of maleic acid?

The second dissociation of furmaric acid and that of maleic acid is shown below :
https://c2.staticflickr.com/8/7775/29482404893_63686e29fe_o.png

After the first dissociation of maleic acid, the hydrogen atom in -COOH group of is joined by a O-H covalent bond and a O...H intramolecular hydrogen bond. Therefore, the hydrogen atom in maleic acid is more difficult to dissociate to a hydrogen ion. On the other hand, after the first dissociation of fumaric acid, the hydrogen atom in -COOH group is NOT joined by hydrogen bond. Therefore, the hydrogen atom in fumaric acid is more readily to dissociate to a hydrogen ion.

Since furmaric acid is more readily to dissociate than maleic acid,
K₂ of furmaric acid > K₂ of maleic acid

pK₂ = -logK₂
The greater the value of K₂, the smaller the value of pK₂ is.
Hence, K₂ of furmaric acid < K₂ of maleic acid