There was obviously ASICS made prior to the 2018 March POW fork, but was there evidence of this for the 2018 October fork?
No hard evidence I'm aware of. The changes this time were made to thwart any ASICs that may have been under development since the last fork. By changing the algorithm every 6 months, this severely impacts the time to develop and ship any new ASICs to market, making it an unprofitable venture. Until we come up with an alternative algorithm (such as the discussed RandomJS), it looks like we'll be changing the algorithm every 6 months to retain the egalitarian nature of mining Monero.