Over the years I have noticed that most alt season started as follows:
1. $BTC pumps first.
2. $ETH $BET & $LTC coin pumps next, leading indicators of the Alt season.
3. Big marketcap tokens next. Usually top 20 on CMC.
4. Then full blown Alt season.
Yes, what you are saying is true, although not completely true, but what I am amazed at is how did you find out about most of the altcoin season? whereas you just entered this forum on August 02, 2020, through which did you pay attention to the Altcoin season over the years? while Altcoin season does not occur every year.