The abuse wasn’t to Stanley Ann Dunham. It was to his second American wife, American-born teacher named Ruth Nidesand, who lived with him in Kenya and divorced him because of his drinking and abuse.
He then went back to Kezia, his Kenyan wife.
Abusive men usual do not just abuse one wife. It is a pattern for them..... Often accompanied by alcohol and womanizing. Sr fits the pattern. It is confirmed in BO’s own words in the Columbian article.