HEVC was finalized in 2013. AV1 was finalized in 2018, and has just finally started getting a robust ecosystem of software and hardware.
Basically, it was the push to 4K (and especially HDR) that caused HEVC to roll-out. In 2016 4K Blu-rays started coming out and they were all HEVC 10-bit encoded. It took a couple more years before dedicated streaming devices and lower-end smart TVs bothered to start including HEVC support as standard because at first 4K content was uncommon and the hardware came at a premium.
Now that it's mostly the de-facto standard, we see HEVC support in basically all streaming devices and smart TVs.
AV1 didn't have any sort of resolution change or video standard change to help push it out the way HEVC did, so it's basically rolling out as the parts get cheaper due to pressure from streaming giants like Google and Netflix rather than due to a bottom-up market demand for 4K support.
Apple ships probably more devices than anyone, and given that the patent pool is huge as mentioned odds are overwhelmingly that it costs them money to support HEVC / HEIC, not the reverse. That theory also is dubious.
Remember when everyone was yammering for VP8 support? Then it was VP9 support? Now it's AV1. Sometimes it takes a while to shake out. By all appearances AV1 is a winner, hence why it's finally getting support.
This is a nit that doesn't negate your main point: Apple may ship more complete devices than anyone, but Qualcomm makes up significantly more of the SoC manufacturer market share[1] at 29% vs Apple's 19%
[1] https://www.counterpointresearch.com/insights/infographic-q2...