Seems to me that he’s trying to do the right thing, as per https://www.aa.com.tr/en/world/us-to-demand-access-to-israels-investigation-of-slain-turkish-american-activist/3331943?amp=1 he’s pushing for more access to the investigation - likely to prevent the IDF from covering it up (and based on the timing this started after reports came in contradicting the IDF’s line).
It’s difficult to understand, but I can see why hasn’t spoken out about it publicly yet - on the one-in-a-million off chance that it turns out the IDF was right about it being an accident all along (yeah right), he doesn’t want to have to apologize to them (and really can you blame anyone for not wanting to apologize to the IDF?).
A silver lining, we can view the US folks who gain access and review as being more independent than the IDF themselves.
That sounds about right for the GOP.
Regarding Dems, I’d have to say citation needed (barring of course the cases I implied above - but in those the reasoning is more nuanced than just “nO mOrE cHoIcEs”). A good counter example is how they backed independent socialist Bernie Sanders, https://www.politifact.com/article/2020/mar/02/how-can-bernie-sanders-run-democratic-primary-when/