Did people really buy STEEM to power up and to sell votes by delegating to bid bots? I doubt that. Practically all the whales were created when STEEM was mined back in mid-2016. They were also the largest vote sellers. It's never been the case that investors have been clamoring to buy STEEM to power up and sell votes.
The price of STEEM seems to move in tandem with the rest of the crypto space. It's simply speculative demand from unknown sources. Much of it languishes on exchanges. Only the liquid part can be bought and sold and the spot price is determined by that.
They bought and held steem to buy votes. The majority of the liquid steem on platform was buying votes.
But if they mostly sold their gains, then there was no net benefit. What you earn from bid bot votes you can power down to buy new votes with. Positive ROI votes can make this profitable after a small initial investment. @likwid allows one to get all rewards in liquid STEEM. That decreases the required initial investment. That precisely is the essence of bid bot abuse, which accounts for a lot of the decline in STEEM's Coinmarketcap rank.