To be perfectly honest, I don't think you could find him guilty - at least not on the evidence used. There is a difference between responsibility and incitement. He was totally incapable of accepting the election result, persuaded his followers that he was robbed and that the deep state conspired against him etc - in that sense he was responsible. But did he actively exhort his supporters to violently riot and possibly even kill elected representatives? Not on the evidence available to the senators.
If it were a criminal case I doubt it would even have gone to trial - at least not without a lot more digging for further evidence.