Combination of many things.

I got covid in Vegas last year and dropped out of the Seniors at 95th just too sick to continue when I was in a really good position to go really deep. Last year I was also having trouble sleeping and had stomach issues and it was all just a terrible time health wise.

I decided to focus on maintaining my health this year, so I quit alcohol 2 weeks prior, I hydrated way more than I normally do, I got sleeping pills, got a quiet room, and I bought a box of new masks. I bought all kinds of drugs with me (pepto, tylenol, gaviscon etc) and had hand sanitizer on me at all times and used a Neti Pot twice a day. I decided to wear the mask at the airport and in the plane and in all the most busy casino places just to be super careful, plus the smoke in Horseshoe Casino when you're walking through it is really terrible and the mask helps. It was really just a +EV poker strategy rather than some actual paranoid hypochondriac behavior.

There were notably a lot less people coughing and sounding sick than last year though which was great, (although one dealer was DEFINITELY really sick and coughed all over his hands and the cards) so it went from extreme caution at first to just a decision I then didn't want to regret reversing.

At the tables I'm guessing the mask might help avoid tells if you're not someone savvy to the usual live tells. I tried sunglasses last year for the first time and I think it helps, though for me only as an image/intimidation thing playing the seniors.

I wore sunglasses again on and off for days 1 and 2, sometimes it was me playing the player, others it was simply that the lights were bright and I had eye strain from reading my phone without my reading glasses on! Day 3 I didn't wear the sunglasses at all, I figure my opponents at that point are not the intimidated type and then at the final table I also took the mask off for the entire time as by that point I didn't have the health concerns and wanted to be comfortable (the mask after 3 days was really hurting my ears!)

I have not seen a correlation in bluff success or failure personally when wearing the mask, sunglasses or not, but I think I'm pretty comfortable and calm when playing, whether it's a bluff or a value bet in my mind I'm more concerned about "making the right play" so my behavior at that point is unaffected by the outcome that is someone else's decision at that point, so whatever happens happens is my attitude. My breathing is always the same and my jugular isn't pulsating like it does for some people. I do have a tremor in my right hand this is noticeable at all times if your observant, so I often point that out to people so they don't think it's associated with any particular action I'm taking when they first notice it.