For the secret power of lawlessness is already at work

2 Thessalonians 2:1-12

not to become easily unsettled or alarmed by the teaching allegedly from us—whether by a prophecy or by word of mouth or by letter—asserting that the day of the Lord has already come. Don’t let anyone deceive you in any way, for that day will not come until the rebellion occurs and the man of lawlessness is revealed, the man doomed to destruction. 

And now you know what is holding him back, so that he may be revealed at the proper time. For the secret power of lawlessness is already at work; but the one who now holds it back will continue to do so till he is taken out of the way. And then the lawless one will be revealed, whom the Lord Jesus will overthrow with the breath of his mouth and destroy by the splendor of his coming. The coming of the lawless one will be in accordance with how Satan works. He will use all sorts of displays of power through signs and wonders that serve the lie, and all the ways that wickedness deceives those who are perishing. They perish because they refused to love the truth and so be saved. For this reason God sends them a powerful delusion so that they will believe the lie and so that all will be condemned who have not believed the truth but have delighted in wickedness.

Why?

Don't let anyone deceive you in any way. And the secret power of lawlessness is already at work.

They perish because they refuse to love the truth and so be saved. Refuse Jesus Christ and refuse to believe the truth will be swept out at the time of the Lord.

How?

Satan is always working on the unbelieved people, and the Lord allows them a while when the day comes all of this wickedness will be revealed and removed by the Lord.