"For this reason,
The reason is the devil and his followers are removed FOREVER from heaven.
There always is joy in heaven; in the past it was over a repented sinner (Luke 15:8-10). But this is different,. It is over the removal of the devil and his followers from heaven. Angels don't have to do the spiritual warfare in high places anymore. There is a new freedom in heaven which is cause for REJOICING.
What a study in contrasts: WOE versus REJOICING. Any doubt that the devil is mean, terrible, and wicked is removed by the use of the word "WOE". However, he still is a great deceiver and master of disguise (verse 9 and 2 Corinthians 11:7-15).
The use of the phrase "and sea" is interesting in that it implies that even evil spirits will experience the wrath of Satan. Recall that water or the sea sometimes refers to the "container of spirit beings". See Revelation 9:14 for a discussion.
The GREAT WRATH is prompted by the short time the devil has. Verses 6 and 14 clearly explain how much time this is. There are three things that are in the devil's future: