I agree with the op that, by some accounts, cryptos became mainstream in 2017 because they gained tons of attention during that bull market. On the other hand, one could argue that Bitcoin (and cryptos in general) still isn't mainstream because only a tiny minority of the world population actually owns it. But as for FTX collapse, I'd actually say it had a pretty minor impact on the crypto market. Bitcoin went down from around $20k to below $17k, but then recovered to $20k+ in just a couple of months. And that was the end of its impact. Then the market started slowly recovering over 2023, so there was no market collapse.
The price impact of FTX only lasted a couple months sure, but to the general public that was Bitcoin and crypto collapsing. There was huge media attention around FTX and all of it bad. Most people don't hear that much about Bitcoin very often, but in the Fall of 2022 and again during 2023 while SBF's trial was going on the average person was hearing about Bitcoin and what they were hearing was that a major part of it had collapsed due to corruption.
This thread is talking about the general public's perception of Bitcoin, not the Bitcoin market itself which of course will always rebound from any bad thing. Heck, at end of last year my mom was very concerned for me because she read an article about the FTX collapse and I was like its fine its just one exchange and the Bitcoin market is bottoming but from what she had read she tried to convince me that this time was different and Bitcoin was collapsing. I laughed and told her it was fine, but this was the effect on the general public who don't know much about Bitcoin. Every market cycle the average person thinks that Bitcoin was a bubble and it's too late to get into it now and now its on its way down to zero. And FTX made a lot more people think that since 14 months ago.
I would guess there are a lot of people who don't even know Bitcoin has recovered and is 3x the price it was after the FTX collapse, because they just assume Bitcoin is still collapsing after FTX. Or if they have heard the price went up some they just assume its a bubble that will pop on Bitcoin's way down to zero. That's the perception of the general public.
Anyway, yeah by crypto becoming mainstream in 2017 I mean that's when most people heard about it. Of course it isn't actually mainstream because hardly anyone has Bitcoin. But I mean it entered the mainstream consciousness in 2017. It went from something hardly anyone had heard of, to suddenly most people having heard of it (and thinking it was some get rich quick scheme), to 2018 when the bear market came most of those people thinking it was some bubble that popped and isn't a legit thing to put your money into cuz it was just a bubble.