Lex had not done it on purpose. Talking to so many Dao Lords, not to mention chilling with a being above the Dao Lord realm inside a hot tub, was extremely draining on his mind and soul. Even the protection of the Host Attire wasn't sufficient when quantity and quality were both against him.
He was feeling incredibly weak, and was forced to call Mary even though he wanted to avoid getting her involved. Yet just as he called her, he seemed to reach his limits and fell. Almost instinctually, he fell towards her so she could support him, yet she was just a projection. She could not hold him up.
He was practically upon her when his brain worked enough to realize he would fall right through her, and teleported back to his office, leaving a reluctant and incredibly awkward Mary, facing a group of Dao Lords who were staring right at her.
