“While we anticipated some degree of business disruption, the new Apple-provided measurement solution did not scale as we had expected, making it more difficult for our advertising partners to measure and manage their ad campaigns for iOS,” Spiegel said in his prepared remarks.
Turns out people care about privacy.
To be fair to apple, the global supply chain interruptions and labor shortages reduces the "short-term appetite to generate additional customer demand through advertising." which loosely translates to companies had empty shelves so didnt bother paying for ads to drive customers to their sites for stuff that isnt in stock