Sober Bertie was much more suitable as king. His wife Elizabeth Bowes-Lyon was popular and they had two charming daughters

Wallis never meant to marry Edward
 
During their photo session at the chateau, Wallis told Beaton that, ‘during the entire period of these discussions [meaning all the meetings about the Abdication] Mr Baldwin held in his possession papers which had been signed by [her] to the effect that she was willing to stop divorce proceedings against her husband.’

She and Ernest had their own nickname for Edward, Peter Pan – a man who refused to grow up. In fact right up the granting of the divorce after the abdication, Wallis Simpson was writing to Ernest Simpson appalled at the direction events had taken and half wishing they could call a halt and get back together.
 
Wallis all but blamed Baldwin for the mess she now found herself in, exiled to a luxurious French chateau, loaded with cash and jewels, but effectively forced to marry a man with whom, as Cecil Beaton recorded in his diary, it was obvious she was not in love.
 
Edward as king was a liability. Edward’s father George V had said ‘my eldest son will never succeed me. He will abdicate…. After I am dead, the boy will ruin himself within 12 months.’ And that was before Wallis appeared on the scene.
 
As king, Edward left highly confidential state papers lying about for anyone – including Wallis Simpson - to look at. He didn’t receive important visitors with respect and seriousness and he offended everyone by failing to go to church – he only went twice in his entire reign.
 
Given half a chance to replace him with his sober brother Bertie, with two small and charming daughters, the government of Stanley Baldwin seems to have had little hesitation. It was a quietly brilliant palace coup.