They (devil and fallen angels) know that Gods vengeance against sin will begin to wake people up to realise it's the end of the world; they will keep saying its climate change etc, we are at the beginning of great tribulation so they are desperate to put everyone in the position so they cannot be saved and they can get to control you or kill you.
The devil and God is in a war. The devil's job is to ensure we are distracted and not aware of what is happening giving him enough time to steal our souls. His war against God is to take God's place in man and to kill, steal and destroy Gods creation. The devil cannot create, he wants to corrupt what God has created so he can use it and feel like God. His efforts leaves man to the same eternal destiny as him, in the lake of fire.