This implosion was something like a massive pressure cooker as well. When the craft’s structure failed due to the immense pressure of diving 12,500 feet, the air bubble inside compressed, causing a massive spike in temperature, roughly 10,000 degrees Fahrenheit: the sun's surface. The video points out that if anything were left, the remains would be gelatinous and expelled through the many cracks and crevices of the damaged submersible. Jack Dawson, I imagine, would've arrived to the ocean floor relatively intact as every cell in his body filled with water and the pressure differential equalized.
Same reason they've found intact musical instruments like violins and pianos in the wreckage.
There was no implosion as the Titanic sank. Except perhaps in some pressure vessels, like boilers or compressed air tanks.
Musical instruments, crockery, etc., would not undergo any violent implosion event. Violin cases are not generally hermetically sealed, especially not violin cases made more than 100 years ago.