By just looking at the video, you can see that they cut the engines after the rocket starts tilting. I guess that’s the flight termination system. Also, it didn't fall into the ground, but into the water.

I've read a lot about this from at least the United States perspective. The rocket wasn't launched from the United States, but the FAA requirements on flight termination is the ceasing of thrust and removing "energy" from the vehicle by rupturing tanks if they pose a danger. The primary thing that's trying to be prevented by flight termination systems is damage/danger to uninvolved parties. So if it's low to the ground simply shutting off the engines is a perfectly fine solution to the issue. If its higher then rupturing the tanks will be needed as it's likely going to land outside the safety area.

The CEO said that it didn't blew up the pad: https://x.com/danielmetzler/status/1906307777242275881

I don't see why would you detonate the rocket if it doesn't pose danger to just fall down. Probably its also easier to collect the debris.

Normally a flight termination system has explosive charges.