There also seems to be a lot of conjecture all over here.

We know that the person arrested "is suspected of involvement in concealing criminal financial flows and facilitating money laundering through the mixing of cryptocurrencies through the decentralised Ethereum mixing service Tornado Cash."

The general interpretation is that they were arrested for development of the protocol and software. It may be that they have them on the hook for other actions, such as assisting particular individuals or directly handling funds. Let's see what comes out of this.

We don't yet know which specific acts they are suspected of.