Even within big stocks the concentration of gains in the very biggest has been extraordinary. Half the gains in the S&P came from just eight stocks; in the first year of the four previous bull markets it took at least 38 stocks to get to half the gains.
The concentration of gains among the biggest stocks is one of three features that distinguish this bull, and is something that typically happens at the end of bull markets, not the start.

Bull markets are often defined as when stocks go up 20%. But a bull market is more than just stocks rising for a bit. In a bull market they should trend upward over multiple years, as they did from 1990 to 2000, 2002 to 2007, 2009 to 2020, and 2020 to 2022, with only brief and relatively shallow drops. 
If this latest bull market peters out, it could turn out to be nothing more than a very large bounce amid the bear market that began at the start of last year.