charting has helped as well, but the song came out in what, 2003/2004? That was long before streaming counted and it has been on their top 100 chart at least one week every year since. Also interesting that it peaked at only #10 on their chart for such a big hit. I think the UK just really really loves that song.
They also broke the record for consecutive #1 UK albums by an international (non-UK) band at 5 with their last album in 2018. Plus Brandon Flowers has seven UK #1 albums when you count his two solo records that went number one as well. They played Wembley a few years ago and headlined Glastonbury this year.
Basically Britain loves The Killers.