Well it looks like Insiders is finally up.
As a computer professional (specializing in web infrastructure), I have worked with extremely large organizations going through mergers, data center moves (or to the cloud) and other extremely disruptive events (like SSO which *everyone* has seen an error for recently).
When you go through a move like that, there are some cardinal rules. 1. End user (customer) experience must not be disrupted for more than hours. You do whatever it takes (including building out new infrastructure) to minimize the customer impact. 2. You never, ever in million years, have incorrect (read: dead) links on your website. 3. Session information must be maintained throughout the site. Side note: I did some work in the 90s for a cell phone company and if you put something in the shopping cart and traversed to other parts of the site, you lost your cart. They lost business and people lost their jobs. That was > 20 years ago.
There is no excuse for the incompetence, not just for MRI, but in general that we see in the way IT performs their job.