Because it likely isn't CP specifically but something close to it that can't be directly called "CP" without giving the other side something to use as "slander" or something.
You're imagining scenarios on the basis of emotionally-loaded language that carries no real factual content. I want evidence of Joe Biden being a human-sacrificing lizard person as much as the next person, but we have to parse each party's statements for what they are saying and what they are not saying, not what we want them to say. They have been very circumspect what is in most of these pictures, why it deserves immediate attention, or whose attention it deserves. Rudy has made it clear he has Hunter's nudes, but they're all being intentionally coy about what's in the other pictures. They could've said, "We saw images of a minor in a state of partial undress, apparently taken without their knowledge," if that's what they saw. Or even, "We saw images of a minor that would meet the standards for opening an investigation when I was a prosecutor." They can be specific without going into gory details, but they choose not to for some reason.
Based on what we know or suspect, there is a mundane explanation for what Rudy is apparently alluding to without description. We know from a former USSS employee that Joe is a skinny dipper. Hunter is reportedly nude when at home, and the minor female wears skimpy bikinis and publishes the pictures to social media. This is a family that lets it all hang out, and there are probably visual records of this all over their devices. For example, if Hunter follows the minor's social media, his browser cache is going to be chock full of underage bikini pictures. (Him and everyone who tried to archive her page last night.) But now I'm starting to speculate about what these mysterious photos are, something I don't want to do.
I don't think so with Bobulinsky. The guy was ex-navy nuclear officer so the highest level clearance he would have gotten in that job was Secret.
Positions can have a minimum clearance requirement, but specific duties may require a clearance higher than that.
Secret isn't that hard, pretty much just need to not have any criminal convictions other than traffic stops and no drug offenses. There is a background check that's extensive but not that extensive.
Any criminal conviction can be mitigated or waived, though the Bond Amendment makes it a little more involved for felonies. And I'm not even sure that was in effect when this guy was in. Likewise, any past drug use can be mitigated or waived, though the Bond Amendment prohibits granting a clearance to an active drug user. If they denied Secret clearances for anyone who had a non-traffic conviction or a drug offense, the Executive Branch would evaporate overnight.