AC/DC has absolutely everything to do with it. The most destructive thing you can do to your voice is constantly push it to sing at the very upper limits of your natural range. The second most destructive thing is using a lot of rasp/drive. Proper vocal technique (something that Axl knows and applies, I got into detail on that a while back) will go a long way in protecting your voice, but not to the extent some people here think it will. Doing what Axl has done throughout his career will hurt any voice.
AC/DC with Brian Johnson material is absolutely insane. Brian was an insane vocalist, to those not familiar with his full body of work, I'd recommend listening to some of his material with Geordie. Once he joined AC/DC and started to sing those songs, his prime was gone in about 3 years. By 83 he was deteriorating. He certainly did a better job than Axl findind ways to keep sounding fine and performing, but his voice has been shot to bits for years.
If you look at Axl, he had his ups and downs from 2012 to 2016 but more or less preserved some of his ability. While his mid range was already shot, he pretty much had, throughout the period, that very powerful, full of overdrive voice at his very upper range. It is on display multiple times in that period, from the US shows in 2012, to TWAT in 2014 in Vegas, and in a lot of the 2016 reunion shows.
AC/DC came, and Axl started to use the voice constantly through whole sets. At the very upper limits of his range, with chainsaw rasp. I reckon that, at that point, it felt relatively comfortable and safe for him to do it. Still, at the second half of the AC/DC tour there were clear signs that he was overdoing it. That voice started to fail for the first time in his career, with cracks and stuff.
It was downhill from there. By 2017, while still somewhat decent, he was a totally different animal already. From 2018 to today, it's a whole new level of deterioration, with a lot of issues that never happened before in his career. Look closely and you will notice that a lot of those involve the upper zones of his range - being phisically unable to sing This I Love, the outro to YCBM etc. Pushing his limits had absolutely everything to with it.
On a positive note, considering the past few years, natural progression would mean him coming out this tour simply unable to sing. The fact that his is reaching the notes again, attempting stuff like TIL and sounding remotely decent indicates that he put in lots of work in the offseason to salvage whatever he has left. We do need to come to terms with the fact that this is what is left in his tank. What he is doing now is much safer, so he might be able to sustain this for a few years.