I posted this in the tactics thread.
This is purely speculation on my part.
AVB is supposedly very meticulous in his preparations.
In the last 2-4 weeks, he and his coaching team would have thoroughly assessed the situation regarding which players would fit into his preferred system and made recommendations to Levy about areas that would need strengthening and possible players that would come in and do the job. I reckon Moutinho was a critical cog in that.
He would have also worked out various permutations and alternatives should some of his transfer targets not been met. He may have been impressed with Bale's skill, pace, power and heading abilities and Gareth has proven he knows where the goal is. Depending on the opposition, injuries or trying alternative tactics, Bale might be the one to replace Ade in the middle with Dempsey coming in on the left side in the front three.