In 2 Thess 2:1ff. it is clear that Paul is clarifying some misunderstandings of 1 Thess. In 2 Thess is a clarification of that. Telling us there will be no one going to Messiah until Satan appears and sets up a deceptive system on earth. Also, looking at 2:6, 7 which have been hard for some to translate, however, if we focus on the subject we don't need to try to insert the Holy Spirit into 2:7 because we are not talking about the Holy Spirit, the subject is Satan. Study the word-always.