Because HE IS God and HE can do, and command, whatever HE pleases.
Disregarding the fact that the Canaanites were engaged in bestiality, homosexuality, infant murder (gee...other than the first one, this sounds uncomfortably familiar), and other abominations - to the point that the land was ready to 'spew them out' - God can do with His Creation as HE pleases.
So around 1450 B.C. to around 1430 B.C. it was bad times for the Canaanites. And then around 400 years later Saul got the instructions to put a hit on the Amalakites (the Hyksos people that 'disappeared' from history?).
Call it a 'clean up on Aisle 4'.
Why the interest in limited 'purges' that were commanded and executed over three millennium ago?
There is an even 'messier' (and eternal) Judgment pending for those not In Christ. That should be the concern. Repeated warnings from the Creator should not be ignored.
Well stated El Cid.
God of all creation and Christ his Son whom he put in control of all creation be praised for His infinite and eternal wisdom.
There are powerful lessons in these passages regarding Judgment.
God not only judges individually, he also judges by groups.
When the Hebrew nation failed to slaughter the entire nation, explicitly noted when some livestock remained alive, Israel was cursed for their disobedience. It wasn’t figurative or a literary technique as the author asserts, but it is very real.