It's unlikely that this went entirely unnoticed for 4 years, and I would guess that when the problem was understood, someone did the math on staying the course,

It's unlikely that this went entirely unnoticed for 4 years, and I would guess that when the problem was understood, someone did the math on staying the course, versus starting over or reversing course. And after all the internal calculations were complete (which factor in way more than technical effort by a small dev team), they intentionally stayed the course. This is probably an extreme example because an internal wiki that is used company-wide will have an incredibly complex and hairy stakeholder matrix (both business and technical), which means consensus is very challenging. At some point the cost of the meetings required to work out a solution (both in time spent, and in time not spent on core work by the stakeholders) probably exceeds the cost of just letting a small team brute-force their way through a bad solution. Cost here isn't just money, it's focus, morale, disruption, conflict, risk, etc.. Keep in mind that you have the benefit of hindsight, and the comfort of looking at it from the outside, with a very incomplete picture of all the constraints and pressures at play.