If you Thanos snapped the bottom 2% of society out of existence, society would become Mayberry with iphones and a small child could traverse NYC alone with no threat whatsoever. People simply do not understand how much low-trust and criminality is tolerated as a political choice.
If you Thanos snapped the top 2% of society out of existence, every company, country, and system along with civilization as we know it would collapse within weeks
If you did the same thing to the bottom 2%, nothing would change. If anything, average daily life would improve