The question has always been how to clean up (all of) the corruption, and have it stay clean.
If Trump cleaned it up, 'they' would regroup, corrupt whatever departments were necessary, and continue their corruption. It's easy for them to corrupt a department or two, as it is a (rather) small job.
But what if the people woke up? What if 'they' realized that 'the people' no longer believed the media? Is it possible to control an entire population when the spell is broken?
What if (nearly) the entire nation (or world) was aware of their evil, and was actively fighting back? Peacefully and lawfully, but actively.
And when/if 'they' continue their obstinate games, what if 'they' (figuratively) found themselves at the business ends of tens of millions of pitchforks?
'They' need to fear us, not Trump.
Waking people up to a degree where they would start taking care of the problem themselves was always the plan...