You download from a bunch of other people at the same time. So if you have a 300mb/s connection and 5 people have the file and are uploading at 20mb/s, it gets a chunk of the file fron each of them, so you would download at 100mb/s.
Besides, you can pause and resume the download as much as you want without corrupting the file. So if youre dowloading a 50gb folder, you can turn your pc off, and continue later. With DDLs, the download link expires and most browsers cant resume downloads properly. Plus if the browser corrupts the download you have to start over. The torrent uses checksums to detect corrupted parts of the file and redownloads just that small part, and in the end you get a clean file.
I made up that speed just to give an example. The thing about pausing/resuming is an advantage of torrents in general, for whoever needs it. Besides, when you download a file via DDL the speed also depends on the server thats sending, which is sometimes much slower than your download speed limit.