So far the only time I've seen that kind of tear or rip in a tube was when I got careless seating the tire bead and the tube sneaked out between the rim and tire. Once that happens it'll quickly develop a bubble and burst, although mine have usually been much more dramatic, with long tears up to six inches or more in length. That happened a couple of times on a rim/tire fit that was too sloppy.
65 psi should be plenty for 700x32 at your 180 lb weight. And flats from bottoming out on potholes, ledges, etc., tend to be snakebite pinch flats with small, slightly elongated punctures on either side, corresponding with the rim.
Is that tube the correct size for the 700x32 tires? Tubes tend to withstand quite a bit of stretching, but a skinny tube intended for, say, 700x18-23 might be at its limits in a 700x32 tire.
Nicking the tube during installation by using a tire lever might have done it. I always use a Kool Stop bead jack to install tires that need more than finger pressure -- much less likely to damage a tube.
And maybe the tube was twisted inside the tire. I use baby powder to slick up tubes and tires. This is recommended by Vittoria and Silca for installing latex tubes, which are tougher than butyl in some ways but easier to nick with careless installation. Their latex tubes now come pre-powdered. I just add similar cornstarch baby powder to all my tubes and tires now. If I'm changing a flat on the road and need to slick up a sticky tube/tire fit I just spit on it.
To prevent the usual tube installation hazards, try inflating the tube very slightly before installation. Just enough air so the tube isn't floppy and shapeless, without expanding the tube. The amount of air is guesswork, so experiment to find what works for you. It's less likely to twist inside the tire, and less likely to be pinched when seating the bead.