Tech Debt is almost always a few things in disguise:
1. Product Failure - The person with the final say on the product has poor taste. They poorly understand the tradeoffs their tech stack gives and how it influences their product. And most importantly they hate their customers and don't understand their needs.
2. Marketing and Sales dominance - The product organization might be competent but they have been driven out of the decision making venues in the company. So marketers and sales make the decisions and hand them down to product to deal with, resulting in tone deft decisions even as the company continues to make good money, the product itself erodes, until competitors arrive and instantly wipe out the business.
3. success and shift - The product, which was initially a success, has stagnated. The product itself was so successful that it created an entire new market with competitors that resulted in commodifying the product. Now the company is frantically looking for a pivot to keep growing the business, resulting in the original successful product drying up even faster.
4. Leadership void - The product was made by a strong, pioneering leader. They might not even consider themselves such a leader, but after they move on, the product fails without their support. The replacement leader might not even be bad at running the business for a time, but eventually focusing on EBITA alone won't inspire people, and the product will erode through churn.
5. Press Release driven development - The company operates by making a moat around its original core offering and they have a semi-monopoly in their space. So the only way to drive more revenue is to sell services that cost more to already existing customers. As a result, teams build products that are made to drive hype cycles and press releases -- once the product is shipped, the major players get promotions and move on to the next exciting product instead of supporting the now-shipped product.