What other measures can a new, non-power user take in order to protect from this type of significant theft, within reason?
For money stored long term, move the coins to a hardware wallet or some form of offline wallet (cold storage).
Use a transaction (rather than importing keys or using an existing seed-phrase) to move the money to a wallet with fresh keys ...
You'll want to set the option -datadir=<path-to-your-drive> either when starting bitcoind, or in your bitcoin.conf file. If you add it to bitcoin.conf, you'll need to restart your node for the change to take effect.
If you want a definitive answer, you'll need to ask him I'm afraid.
My best guess is that Windows development was the thing he was most familiar with (or even only familiar with). The coding style was also similar to one commonly used in the 90's by Windows developers.