Why did Paul take money from the poor Macedonians instead of the wealthy Corinthians?

Paul took wages from other churches in Macedonia so he would not have to take any support from Corinth. Although Macedonia was poor and mountainous, he chose to receive offerings from those poor believers rather than take a dime from wealthy, commercial Corinth while preaching God's gospel freely.

Les explains that Paul, perhaps against his better judgment, actually took offerings from those poor people in Macedonia. Greece is mountainous, usually with very little means of making a living or growing crops, so that area was poor and destitute. Nevertheless, Paul took money from that poor region so that he would not have to take a dime from Corinth, which was a wealthy, commercial city. In 2 Corinthians he speaks of taking wages from other churches to do the Corinthians service, meaning he received support from other areas of Greece rather than from Corinth itself.

2 Corinthians 11:9

And when I was present with you, and wanted, I was chargeable to no man: for that which was lacking to me the brethren which came from Macedonia supplied: and in all things I have kept myself from being burdensome unto you, and so will I keep myself.

Were there wealthy people in the Corinthian church?

Yes. The Corinthian church included well-to-do members. They demonstrated their wealth when they mishandled the Lord's Supper by bringing expensive foods and wines, while Paul chose not to burden them financially and instead received support from the poor Macedonian brethren.