The idea is that IPA displaced the water and then evaporates much faster. Contact cleaner may do that but IPA is about 100x cheaper and is known to work.
The downside is that you put your phone in rice. The best option would have been to turn the power off, then clean with IPA before you powered it on and for sure before you connected a charger.
Here is iFixit's video on water damage. It will explain a lot.
https://www.youtube.com/watch?v=DsDpALKQjUQ