i was surprised to see the market today, everything fell in a short time, bitcoin fell around $1000 very fast and looking at coinmarketcap, all coins are red. a few days ago bitcoin rose slowly, but today was very surprising. What happen today?

It's just another day of "correction" as you cannot predict when will it be exactly happening.
Looks like the BTC bulls cannot keep up to sustain a certain range which results for the market to go down a bit.
As of today, we are still in the bear market so these mini bull runs are just short term only. We just don't know when will the market go up again. It's unpredictable.
Bitcoin is struggling to break 33k but it's rejected always time and after every rejection, btc dump little. major altcoins are not raising because btc price is not stable. Market will green when btc remain stable for atleast 48 hours. The real bullish season will start when btc stable above 32k.
These downfall after some rise are short term correction which is normal in crypto market and nothing to be worried about that. crypto market is unpredictable but i hope we will not going to bear market as we are not recovered from bear market yet and now its time for bull now