A explosion of a 60mm mortar shell inside the car would have killed everybody instantly and ripped half the car apart. Thats about the smallest size of mortars. Thenthere are rifle grenades, which are smaller but also make a bigger explosion than whats in the video. Also, both types have complicated fuse mechanisms. They wont detonate if you just drop them, they need to get launched first. Thats a safety feature.
Like I said earlier, I think the "bombs" were made especially for that use. If you can deliver them so precisely, they dont have to be big. Those guys in the car are not fighting again any time soon. Other Russian soldiers will have to take them back to a field hospital, where they get treatment ect. - that way this tiny bomb keeps a dozen people busy and prevents them from fighting. That is more efficient than just blow them up and kill them.
We are witnessing the next step in drone warfare in Ukraine. No need for super expensive sophisticated drones anymore, that are basically remote controlled airplanes. Today the drones can be operated by any soldier with a small hand held controller.
And next we might see stuff like this:

Btw., drones dont always have to fly. It can also be a small vehicle like a RC car, that waits next to a road, and if a tank comes along it drives underneath and explodes. All just a matter of money.