How did he know

I have played off and on with males since a young age, got married and divorced once and had numerous girlfriends before and after my marriage. But when I was between girlfriends I would seek out guys at book stores or cruising spots to suck off or get fucked by.
My family and social circle had no idea I liked having gay sex, still don’t to this day. After my last girlfriend 5 years ago I decided I only wanted cock and been pussy free since.
Well I’m straight acting while out in public and no one would guess I love cock. I was at a local Walmart doing some shopping and was looking at a few things in the tool section when another guy came into the isle and was looking for something, he got kinda close and asked me where the pipe wrenches were.
He was in his early to mid 60’s with a dad’s bod, not bad looking and clean shaven. About 6’ and about 230 lbs.
Myself 65, 5’6” and 135 lbs. he went to where I pointed and as I was looking for what I wanted I caught him checking me out a few times but didn’t think anything about it.
I went about my shopping and didn’t think about it. As I was in the self check out he came up to the check out next to mine and once we were both done we were walking out and when we got to the parking lot he thanked me and was walking the same row I was.
We chatted a little bit and we were parked a couple cars apart and he said he needed to grab lunch and asked if I wanted to join him.
I was thinking about lunch so said sure. We go to lunch chat about all sorts of things, when we got ready to leave and in the parking lot, he showed me because he just boldly asked if I would go back to his place and give him a blowjob.
I paused for a few seconds ( maybe 30) and then told him why not. I followed him home which wasn’t to far got in the house, he walks over to his couch and as he’s getting ready to sit, he undoes his pants and pulls them and his underwear down and then sits down.
He said he really need to get off but was tired of using his hand. I looked at his cock, cut about 61/2” and average thickness. I got down on my knees and grabbed his cock, stroked it a little then went down on him.
I sucked him about 5 minutes or so when he said he was going to cum. I continued sucking until I felt him start to pulse and blew a good size load in my mouth.
After swallowing and finished cleaning his cock with my mouth Ingot up and was getting dressed I asked him why he asked me to blow him… his answer shocked me as he said “there was just something about you that I guessed you were a cocksucker”
To this day it still baffles me as what signs I gave off to make someone think I suck cock, not that I’m complaining and yes I sucked him off numerous times until he moved to FLORIDA.