为什么BeautifulSoup findALL（）方法返回空列表？

Question

我想解析该Div标签，但返回空列表

from bs4 import BeautifulSoup
from urllib.request import urlopen


url = "https://en.savefrom.net/#url=http://youtube
.com/watch?v=lZ5h_Xg4Btg&utm_source=youtube.com&utm_medium=short_domains&utm_campaign=www.ssyoutube.com&a_ts=1553333088.288'                                                             "
req = urlopen(url)
page_html = req.read()
soup = BeautifulSoup(page_html, 'html.parser')

这将返回空列表

x = soup.findAll("div", {"class":"def-btn-box"})