Breaking ground doesn't mean they were installing the foundations. They probably had a ground breaking ceremony, then waited a month or two for a permit. After that, they will find some exist utilities that don't appear on any as built drawings. They will need to wait another couple months for which ever public utility company to come out and move their shit. Once that's moved, they can start installing the shoring while excavating down about five stories. This will take a few months. After this is done, all the equipment will need to be mobilized out. Now, there will likely be some review comments on the structural submittal to the city. They'll have to resubmit before getting the foundations permit. After getting the foundation permit the foundations subcontractor will install some test piles. Those test piles will need to cure for about a month. Once the piles have cured they will be tested and the report will be sent to the geotechnical engineer of record. The foundation design will then be approved or redesigned based on the results. After all of that, the foundation subcontractor will come in and install the foundations. This will take a month or two.

Throw in some financial delays, issues getting one of the shoring/foundation/grading subcontractors in because the delayed schedule no longer works with their other projects it can take a few years. Once the project is out of the ground it becomes much more routine as all the permits are in hand and the schedule is much less likely to change.