Or HaChaim on Numbers 16:27/אור החיים על במדבר ט״ז:כ״ז

1 ויעלו מעל קרח ודתן ואבירם, They lifted themselves up from the residence of Korach, etc. The effrontery of Datan and Aviram in continuing to maintain a defiant posture though they had already been abandoned by their fellow travelers who had withdrawn in fear of being punished together with them, made a suitable impression on Moses so that he announced that the people would witness Divine intervention by the manner in which these people were going to die. This was to prove that he had not appointed himself as their leader but that G'd had appointed him at the time. The words את כל המעשים האלה mean that everything Moses had done including insignificant appearing things were all carried out at G'd's instruction. He now said that not only would these people die immediately but they would die a particularly gruesome death.