Compare stability of 1 and 2:
1 is more stable than 2.
- Both have the same number of π-bonds.
- Both have one resonance structure.
- Both are non-aromatic.
- In 1 there are three α-hydrogens, whereas in 2 there are four α-hydrogens.
As extent of hyper-conjugation is more in 2 than in 1, making 2 more stable, which contradicts the answer.