what kind of things need to be true for this to happen?

One courier bot earns ISKs enough to pay for 4 accounts. I made my own statistics last May and bot made 2.98kk. I did not make whole month statistics for miner, but this is obvious that miner do more ISKs then courier. You need any mining barge fitted with t1 strip miners and setup traveling route between 5-6 systems with 10+ belts per system to have plenty of ore. It is a good idea to create 300km bookmarks if you mine in 0.8-1.0 systems to warp to the nearest asteroid from 300km bookmark. 12 hours a day splitted into two big 6h intervals to avoid ban.

My miner with perfect skills earns about 1.2b a month. That's not even close to what your suggesting. Although I never used the traveling feature so that might be the problem. Do you recommend using the "No profitable bookmarks left" or "by timeout"? Also if there will be many bookmarks with the same name how will the bot know which one to use? I assume he'll target the top most bookmarks, since bookmarks from the current system are moved to the top?

If you frequently see that bot is logged off and waiting for DT (multiple Sleep-s in the log) you may need to setup traveling and switch systems to find ore. Using timeout is better I think.

I should also remind that VMWare is not officially supported. Depending on internet connection and guest system you may have errors like asteroids not visible in overview when uing VMWare. 1.2b/month for miner means you have some problem and bot is not functioning correctly.