Surely something must have motivated him to go to Real Betis. Sometimes there are factors we don't know about in the decisions of players and coaches. For example, Mourinho refused to go, despite being overpaid, to play in the Arab League. Maybe his wife doesn't like the climate or something else in that part of the world.
He has already experienced playing in La Liga, particularly at Betis, although it was not for very long as he was only on loan for half a season. However, the atmosphere, support, and chemistry between Antony and his fellow players and coaches were quite good, and it cannot be denied that his performance improved compared to when he was at Betis. Therefore, it is quite reasonable that Antony chose Betis without hesitation.
He could have chosen to earn more money in the SPL, but that would have slightly diminished his career popularity. While it’s realistic to prioritize earnings, he still aims to achieve significant success in the end.
All choices ultimately rest with the player in this case, as not everyone prioritizes money or seeks out a big club. If the fit isn't right, it can hinder one's career, and he has already experienced that at Manchester United. Therefore, he seems determined not to make the wrong choice again moving forward.