Senior management (i.e.: those with true P&L responsibility and strategic decision making authority) need to be made aware of the business impact of NOT acting and the costs associated with taking action. If there is truly a valid business case (and there often is), and the costs do not exceed their ability to pay (the company must have money or be able to find money to pay for it), then they will want to take action. Their next questions will be about "how to" do it.
This where it pays to have some outside help. Internal resources are often inexperienced at managing changes of this nature. In many cases, they've been in one environment for a long time and haven't had to lead a change. They are managers (keep the boat steady), not change agents (rock the boat). Outsiders or new managers in the roles are often brought in with a mandate to rock the boat.
In all likelihood, if the ones making the case are internal, they are in a difficult position to explain "how to". Consider that if they really knew "how to", then their bosses might ask, "why didn't you say so sooner?" or worse, "why didn't you do something about it sooner?" If the one raising the concerns is new, he has an opportunity. If it's someone who's been around awhile, then he may be fearful of making a career limiting move. This latter type is often in the way of change and is one of the reasons why the organization has a problem in the first instance. If I'm brought in by senior management (e.g.: executive branch, operations, finance types), then I often find this to be the case - the manager is part of the problem. If he can admit it to himself and get on-board, then there's some chance, but if not, he's probably not going to be around for long. Admitting one doesn't know and has now learned, is far superior to resisting change.
Silos are a problem and often a hidden one. Again, outside perspectives are often needed. Silos are hidden by the very reports and KPIs meant to reveal how we are doing. Problems within a silo are usually well known within the silo, but hidden from outside view. Hiding them are reports and indicators meant to reveal problems so they can be acted upon. But by revealing problems, one risks appearing to be doing a bad job.
Even if there is knowledge in-house that communications are an issue, there is usually little real knowledge of the impacts. Performance reward schemes often exacerbate the situation here. It takes a dispassionate outside perspective to look into this and highlight the flaws. It's very challenging for one who receives a bonus based on a performance measure that is flawed, to want to change it, especially if it's been good to them. I've experienced HR departments staunchly defending their reward / bonus schemes, even if they know it's not really encouraging behaviors that are desirable. They often don't have the insight into behavior at the more granular level to consider any other options, and they rarely have help from those in the other departments and areas where behaviors need to change.
Silos produce reports - often looking good inside, but hiding what's really doing on inside. One thing that many senior managers know exists, but struggle to see clearly, is the obfuscation of truth in what is being reported to them. Reports and KPIs often show a somewhat sanitized view and since they are allegedly based on data, they become believable (or at least provide for plausible deniability). Data is often flawed though and anything based on what's in databases that is not truly fit for purpose, will be likewise flawed. Again, it's often not in the best interest of many managers to point this out. Imagine telling your boss, "here's your report, oh and by the way, I'm pretty sure it's fictionally based on what we have in our flawed data base". Reports might be one manager's responsibility, data storage another's, data input yet another's. Everyone owns it, therefore no one really owns it.
I'm all for making evidence based decisions, but the data better be rock solid - and sadly, it usually isn't. I could go on about this one.
Bottom line - unless you are brand new, have a mandate to rock the boat, have the cross-functional experience to see through all the elaborate smoke-screens, then get some help. I hope I've answered your question.