Trump was mulling over running for president since the 80s. There is video proof. He was directly asked in an interview if he planned on running for president some day. It was not inspired by any Russia trip. It has been well known for decades that trump considered running for president. He even started a "presidential exploratory committee" in October of 1999. Then he looked into running both in 2008 and 2012. People were urging him to run in the 80s as well.