In a number of cases in the past, Apple has financially backed suppliers to increase manufacturing capacity for some product line Apple was interested in, because Apple wanted millions of that part, at tight tolerances, and the company could only produce perhaps hundreds of thousands. In exchange for paying for the buildout, they get a permanent Friends and Family discount on that manufacturing line. Lately it seems they've opted instead to pay for preferential scheduling on the backlog.

Because Apple has super deep pockets and TSMC is a for-profit corpotation with shareholders

To over simplify again, your biggest customer always get preferential treatment. It really is just business, and nothing to do with industry.

Apple buys capacity by by paying TSMC. What it means is that they pay to get preferential treatment for certain chip runs.