We added a filter that converts youtube iframes into a <lite-youtube> element, which avoids loading the large amount of JS that the youtube player needs during page load. In some cases the filter is not being applied, which brings down the PageSpeed scores to a very low level (some cases around 20/100 where it would be 40 to 50 otherwise).

e.g. https://www.greenpeace.org/southeastasia/ I verified that this site does have the lazy youtube feature enabled.