Because, with respect, unlike most Spurs fans and posters on here, I have been following this project very closely from the very beginning.
This was a complex build because it is a huge, state of the art, new stadium; two thirds built around a still used, existing stadium; on a site with limited space; in a built up, populated area with poor access. The vast majority of similar new stadia around the world are built on large, open sites with comparatively easy access.
The build was further complicated by the inclusion of a never before attempted, three section, two directional sliding pitch (which will reside under the stands while retracted) with a second pitch underneath it.
As to why it was a tight schedule, well the last ever game at the old Lane was in early May 2017 - which gave Mace and Spurs 16 months to demolish the old stadium; dig foundations; build the remaining third of the stadium; install the roof; build and install both pitches; build the podium; and complete all other public access areas surrounding the stadium. A tough ask. Doable, with a fair wind. But challenging. And, but for the serious issue that came to light last week, Spurs were on course to host the Liverpool game on 15th September. Close. But no cigar.
Between them, Mace and Spurs have failed to hit their ambitious target but anyone who claims that that is evidence of a poorly managed build has little knowledge or understanding of major construction projects - almost all of which are delivered late.