How is it true? My clients just show me what the people I follow publish; or do you mean that popular accounts get more kind:6s thus the people I follow give some popular pubkeys a disproportionate amount of visibility?

You, and other Very Big Npubs, have a completely outsized impact. It's like the Elon effect, but there are 20 Elons. You have over 600k followers. Even supposing only 10% are "real and active", which is very low, if you boost or quote something, it will likely trend because it ends up in 60000 npubs' feeds. If I do the same, it ends up in 70 npubs' feed. Everyone is looking at what you are looking at.