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.