I'm wondering what I'm doing wrong or can do better when I clean my bike, specifically my drive train.

I do a wash every so often, which includes scrubbing the chainring, gears and chain to a point that it looks free of grease/oil. I let that dry and the lube the chain w/ Wolf tooth lube. I also use WD40 (reg one) on the moving parts of the derailleurs, being careful not to get it on anything else. For degreaser, I use a diluted simple green (reg one).

Here's the question. After just one ride, my chain and gears are coated in black, assuming it's grease. I figure it should take a bit longer for my drivetrain to look that dirty. Am I doing something wrong? Am I really not getting my chain as clean as I think? Any advice?