Humans are creatures of habit and often guilty, unintentionally, of lapsing into patterns that can, and often do, adversely impact many areas of their lives. As youngsters we tended to resist responsibilities and when allowed to continue, soon learned rules aren't for everyone - "if you're smart." When such patterns were allowed to develop, and as we grew older, we began to look for short cuts in every task we faced, no matter what, or whom, we had to use, in doing so.
The 'Velvet Rut' is where you find yourself in an unfulfilling job in which you are not learning anything new, not using the full extent of your skills and are just bored stiff. You probably disconnected several months ago and are now just going through the motions. The work is no longer stretching. You can do most of it with your eyes closed so you are unlikely to get fired for poor performance. Your level of competence and familiarity with the job means that, while it is not exciting, it isn't scary either. You are pretty much marking time. The difference between the 'Velvet Rut' and any normal rut, is that the pay and benefits are very good. You couldn't get the same amount of money for such an easy life anywhere else.
The longer you stay, the more comfortable the environment becomes because you know the organisation inside out and can therefore work the system. You thus minimise the risk of anything unexpected happening or of being faced with difficult situations. Seniority and good relationships leave you well placed politically, so the pay rises and good bonuses keep coming. You are also too expensive to make redundant because of your long service. You might feel as if your brain is shrinking and sometimes want to scream at the tedium and banality of it all but, in the final analysis, they are paying you way too much for you to pack it in and do something else.