Both lost significant deposits from crypto blow-ups, reducing their liquidity and tanking their stock prices [1]. That left them uniquely vulnerable to both perceptions [2] and rates (as they sold the short-dated, liquid, low-duration assets first to plug the crypto hole).
"The bank’s digital-asset clients represented more than a fifth of its deposit base, and Signature’s executives said in December it would work to shrink that without leaving the space entirely. Earlier this month, the company reported it had pushed out $1.5 billion in funds from crypto platforms in the year’s first two months, while taking in $682 million in regular deposits. By then it was touting all the ways it wasn’t handling crypto in a presentation.
I read the article and it never establishes a causal chain.