Early mobile networks were slow and data was expensive. 3GP files were highly compressed, making them small enough to download over 2G and 3G networks.
Most of these old "free download" sites have been abandoned, hacked, or taken over by malicious actors. If you visit the domain today, you are likely to encounter: www-3gp-king-masti-com
You don’t need to risk your device’s security for compressed videos anymore. Today, streaming services offer mobile-friendly data-saver modes: Early mobile networks were slow and data was expensive