I don't think the intent was to control Trump as much as it was to control the narrative and box him in, which worked very well with the support of their co-conspirators in the MSM. The couldn't get him to do much, but they definitely stalled his administration and prevented better staffing choices.

released a set through Wikileaks to show they were serious. That may be true, but it could also be that they simply fed the info in like they tried to do with everything else in Russiagate. The entire process has CIA written all over it.

So, now think through why didn't the DNC let the FBI have access to the server to "investigate"?

You're probably thinking they did that to avoid the FBI getting more dirt on Clinton for control. I think it's more of plausible deniability for the FBI, which was basically in on it all. We already know this based on their actions and lies. FBI refers to CrowdStrike's assessment on the server, wipes their own hands of the issue while giving Clinton a clean slate on it. If the servers or evidence is ever uncovered, FBI points back to CrowdStrike and denies knowledge or involvement. FBI could have gotten warrants for the servers if they really wanted to. I don't think they ever asked for access.