For one thing, stablecoin issuers hold more than $100B of US treasury bills, on the same level as some major countries. For better or worse, the old and new systems are interconnected now.
https://www.brookings.edu/articles/the-rise-of-stablecoins-a...
$100B sounds like a lot of money to any sane human being, but for the T-Bill market it's really a drop in the ocean. Current T-Bill Market cap[1] is 29 Trillion give or take a little, so $100B is about 30bps of the total. Would nudge the market a little bit, but not that much.
[1] Here's my source and they should of course know https://fred.stlouisfed.org/series/MVMTD027MNFRBDAL