In a HTML table, unless given a fixed width, the width of each column depends on the natural widths of all the columns, and those widths depend on the content of every cell in the column, and those cell natural widths depend on word-wrapped layout as well as other layout of content in each cell, including nested tables recursively.

In other words, with default styling you have to calculate natural widths of every cell in the whole table before you can begjn layout out even the first cell of the table.

There are style settings you can use which change this, and allow layout of early cells or rows to complete without depending on later cells.

(Also the height of each row can depend on the height of the content of every cell in the row. But that's local to each row so it's a relatively small dependency.)