Bear market doesn't happen because there is futures, bear market is a natural trend in any markets including bitcoin. But you also have a point here, there has been a lot of market manipulation that is taking advantage of futures.
In fact over the past weeks I have noticed spikes in number of shorts whenever price starts rising up (not falling!) which will then prevent that rise. Good news is that even though the amount of shorts is increasing their effect is drastically decreasing:
Because futures market is essentially a gambling market, as well as most of derivatives,,, a lot of them are traded without real money or just upfront contracts that are owed money, so there is a big part of traders who actually bet without putting money down, and then they go and try to move the physical market to win their futures bet. At least this is how it works with stocks but I guess same as crypto now.