Its mostly coming from Revelation. If the signs are fulfilled then the second coming is now a possibility whereas before that it’s not. I remember growing up in the cult there was news about a dam being built in the middle east which got everyone hyped because that could be the catalyst for one of the signs since in theory it could change the flow of a river…

One of the other things called out is Israel being beset from all sides by the world or something then the 40k elect will show up and you get the second kingdom or something. Idk been a while since I read Revelation much longer since I took it literally