Having lived through the early 8-bit home computer era as a teenaged user and then in the mid-80s working in tech startups making hardware peripherals for 16-bit computers - although not as a hardware designer, here's my perspective. Early digital devices definitely could occasionally cause interference with TVs and radios in their immediate area, so there needed to be some regulation to address the issue.
However, once aware of the potential problems it wasn't too hard or even very expensive to design hardware which avoided the most serious problems. Properly grounding components and a little bit of light shielding here and there would generally suffice to ensure most devices wouldn't cause noticeable issues more than two walls and 30 feet away. I think by the 90s the vast majority of hardware designers knew how to mitigate these issues while the evolution of consumer device speeds and designs reduced the risks of actual interference on both the 'interferor' and 'interferee' sides.
Unfortunately, the FCC's regulatory testing requirements didn't similarly evolve. Hardware designers I worked with described an opaque process of submitting a product for FCC testing only to receive a "Pass/Fail" with no transparency into how it was tested. Sometimes the exact same physical product could be resubmitted a month later with zero changes and pass. This made things unpredictable and slow, which could be a lethal combination for small hardware startups. So there emerged a sub-industry of "independent RF testing labs" which you could pay to use their pricey gear and claimed expertise to test your device and tell you why it failed, let you make a change right there and retest again until you passed. This made things more predictable but it could cost upwards of $10K (in 90s dollars) which was a serious hardship for garage startups. I was told a lot of the minor hardware changes made during such interactive testing probably did nothing to decrease actual interference in the real-world and only served to pass the test.
Then came the era of "weaponizing" FCC certification. Small startups could avoid the costs and delay of FCC testing by filing their product as a "Class A" device (which meant only for use in industrial/scientific environments) instead of as a "Class B" (consumer) device. The devices still had to not interfere but their makers could self-certify their internal tests without going through FCC testing. When new hardware startups would threaten a large, established company product with a cheaper, better product shipped as "Class A", BigCo would report them either interfering or just being used in consumer environments - despite the device very likely not interfering with anything. This ended up creating a lot of problems for such startups because if their cool new product ended up even once in an arguably "retail distribution channel", they could get hit with big fines - all without ever causing any actual interference - and even if the device was able to pass FCC testing and would have been certified as Class B. It got especially ridiculous when a lot of cheaper products were simply generic designs, like a modem using the standard Rockwell chip set and reference design. These were often made on the same production line and even used the same circuit board in a different case as other products which all passed FCC testing. But if you didn't have your official "FCC Cert", you could get busted.
I left the hardware space in the early 2000s so I never heard if these regs were ever modernized, but it sure seemed like they were in need of it.