It is the combination of the number of comments he has created, editing them (which takes a similar number of RC credits as the original comment), the bulk voting, powering down, and the relatively low amount of SP on the account.

All those actions ate through the RC on the account. The main thing was a new power down week started which means another chunk of SP was reserved for the weekly power down (which means it reduces the voting power and resource credits by whatever is being powered down that week which is 39.432 STEEM). This likely was unexpected behavior which made a sudden and quick drop in the already low resource credits.

No one took any resource credits away. It just isn't technically possible without a hard fork.