Really? There isn't a single group of people more motivated than the Scientologists who've tried to infiltrate the US government?
The US government is the most powerful institution in human history. It controls more money in a year than the totality of almost every other individual country's annual GDP. It can kill billions of people in a couple of hours. The power here is staggering.
And the Scientologists with 5k agents is one of the most serious attempt at getting into the guts of that and corrupting it? Seems unlikely, somehow. I'd suggest that the Scientologists were just crazy enough that the conspiracy was unwound. US federal politicians have a totally reasonable and expected corruption problem; this probably isn't one of the most major attempts. The US army routinely purges countries, purging unfavourable records is just so small-biscuits it is hard to believe.