If you have noticed, since last 3 to 4 days bitcoin market started showing the bullish market and today it stayed above $51k levels with decent volume which will definitely disappoint those people who lost their belief on getting into $100k levels; anyway they are still having time to re-join the party.
I am stunned at OP question that when bull market will start? I mean what else value Bitcoin need to take to convince people that its bull market now. Right now bitcoin is at 51k and for last 6 to 7 months bitcoin is trading above 50k. IMO people who have bought BTC at ATH are looking for this 100k target to get there profit.
What happens is that people are mostly interested in trading very short time frames, it is obvious that if you zoom out your trading chart you will that the market has been going up for more than a year, we have seen some corrections along the way but this is natural and it is to be expected in any bull run regardless of the market we are taking about, still another reason is that people are just that greedy and they do not care about all of that growth we have experienced, they still want more profits, and as such any slowdown of the growth of bitcoin or a correction are enough for them to think the bull market is over.