To simplify - The majority of employees have followed the company's guidance.
Let's break it down.
Our starting point is "more company employees than not have believed and practiced what has been preached, from humility to going to the source"
The first problem is putting a descriptive term into the middle of an idiomatic phrase. More < something > than not is a common idiom. More often than not is a common form of it, which indicates "most of the time, but not all of the time". In this sentence, company employees belongs in the < something > space; you could make it just "employees". So more employees than not have... indicates that most, but not all, employees have done this thing.
believed and practiced what has been preached is another butchered idiom. Practice what you preach is the idiom here. It means that a person who tells someone else what to do should be expected to do it themselves. A doctor who smokes and doesn't exercise, for example, might be told to practice what you preach. In this case, the idiom is being misused. It is talking about "what has been preached", indicating that this preaching is coming from somewhere other than the employees themselves.
With that understanding, then, we can see that it's trying to say that the employees have believed and practiced the advice they received.
The last part, from humility to going to the source, is yet another idiom. This one is from A to Z, which is used to refer to everything between two points. It doesn't entirely work here, because the two items listed - humility and going to the source aren't parts of any obvious series.
So, all things considered, this appears to be a rather mangled attempt to use idiomatic language to say something fairly straightforward - the majority of employees have followed the company's guidance.