Despite the claims to "uniparty", the Establishment Republicans really ARE NOT Democrats nor aligned with their party establishment. If you look at the legislative history of when the Republican Establishment is in control, you'll note there's actually a LOT of issues where they and the Democrat Establishment differ.
For instance, federal funding of abortion. Say what you will about the R establishment not being aggressive against abortion, but they have very VERY consistently maintained things like the Mexico City Policy and other anti-government funding for abortion measures, not simply maintaining them, but REESTABLISHING them when the Dems end them. Gun control is another issue like that where the Rs generally don't push anything. Green matters is another big area where the two Establishments depart ways rather dramatically.
Why is this? Because the R establishment WANTS power too, just like the D establishment, and they know they need to at least do things to support what their base wants. Beyond that much of the R establishment is ACTUALLY pro-life, they are ACTUALLY pro-gun, etc. They just want power more than they want to see those things come to pure fruition and so they tend to not pursue objectives that could have major backlash and cost them power.
Which brings us back around to this Jan 6 commission. Between its remit and its schedule, it was a blatant ploy by the Democrat's to keep the riot on Jan 6 in the forefront public consciousness for the 2022 midterm elections. The Jan. 6 riots are seen to be damaging to the Republican Brand in an election that appears to be otherwise shaping up very favorably to the Rs. The R establishment wants power back, thus, they will seek to squash constantly bringing up Jan 6 as much as they can. You'll note that the Rs who voted FOR it are the ones who's personal influence and power is not as much tied to being in the majority, and, in fact, their power might well DECREASE if the number of Rs increase in the Senate, as the closer things in the Senate stay to 50/50, the more power the squishy Rs have, but the larger the R majority is, the less the majority has to depend on them and the more they have to fall in line.