It's worth noting that this attack that the IDF refers to in this video is not the same attack that has reportedly killed 70 Palestinians.
The
FT have conducted an investigation into the one that is believed to have killed 70 Palestinians en route South Gaza and concludes that the "evidence points to IDF weapons."
They state that "analysis of the video footage rules out most explanations aside from an Israeli strike," and Chris Cobb-Smith, a former British army major and weapons and munitions expert also states that "the available evidence suggested the most likely cause of the blast was a missile strike."
There are also explanations as to why there's no crater, which I've seen referenced as a reason for doubt earlier in this thread, as well as why it's unlikely to be a car bomb.
I get the intuitive assumption that Israel wouldn't have anything to gain from stopping the evacuation, but let's be real there's a lot of evidence that armies often act in irrational ways in a war, especially when there's such an intense bloodlust as we've seen on display in the past few days.