This is just down to the charts reporting streaming as well as sales now. Nobody is buying records, so now every time a track is played on YouTube or Spotify etc, it's reported as some fraction of a sale.
So when a track from some years ago gets featured on a viral TikTok video, or in a commercial or movie or TV series, it will often pop back up in the charts. Every Christmas, various holiday songs chart for a similar reason.
At the time of writing this, Harry Styles has three songs in the Billboard top 10 and 13 in the Billboard top 40. He released an album, and his fans are streaming the album in their millions, so his album tracks are charting. In some countries, getting a song into the chart is used as a form of protest - in Britain, various rude songs about politicians and members of the royal family periodically end up in the Top 40. Needless to say, Boris Johnson is a F**king C**t and Prince Andrew is a Sweaty Nonce do not rely on radio airplay to chart.
The charts are not what they were, in that you don't need to release a single (either into physical stores or onto music sales services like iTunes) to get into the charts - so any comparisons to the charts of the 2000s, 1990s, 1980s or prior are not really valid.