As promised I took some pics.

This table is one I remember my mom refinishing when I was maybe 7 years old? Just old enough to remember as an event rather than a fragment and to understand what she and dad were up to but not yet old enough to help as opposed to get in the way. Most of our furniture was on the old side, but now that I know what I'm looking at, only one piece I've seen was either hand made with hand tools or genuinely antique. Just as well, because I'm the only one in my family who can pack a truck well enough that nothing gets damaged (and that took some years of practice).

On to the pics. First off are a couple views of one of the leg/rail joints that are still sound:

I've never seen a cross brace attached like that, with the odd round tenon sort of thing. Clearly machine cut, probably in a factory machine that had two cutters staggered in line so it could be done in a single pass. That would be a bear and a half to set up in a small shop and have it come out right. One thing I noticed right away is that all the braces are made of two pieces and the proportion between those two pieces is consistent.

Here's the failed one with the leg removed. I thought this would be pretty easy to fix until I started looking at it. Before I took the top off, it seemed like just make a new corner brace and duplicate what looked like an odd inline tenon into an angled mortise on the rails. Then I saw those round tenons.

A bit more poking around shows why all the corner braces are two pieces and why this looked like a normal, if unusual tenon arrangement when viewed from below:

I'm not sure why they did a straight tenon on the bottom piece. It's too stubby to have much strength vs the top piece that locks everything together.

Since whatever glue was holding this together has failed my plan was to take it apart and re-glue, but the round tenon does not come out easily. I have the distinct impression that both tenons are dry joints, with the only glue being that which holds the two brace halves together. Plan failed because I couldn't budge the other side out of place without breaking stuff.

On to plan B:

I like brass screws, it's weird I know. The steel screws are what I had left over from removing the top. I was replacing them with some round head screws (flat underneath, better for a pocket hole holding a top down - better still with washers, which I forgot to buy).

First I screwed the two halves of the brace together. I tried to get some 5 minute epoxy in there but I don't think much of it got into the joint. Then I cross screwed the side where the tenons didn't stay in place. I don't want to call that round hole a mortise, but I guess that is what it should be called. Anyway, the top piece that is supposed to lock the joint wouldn't stay in place.

Once this was done, the leg locks in well without bottoming the nut on it's hanger bolt - which is how it had arrived, nut screwed right down to the bottom of the threads and still wobbly.

All done.

Man do I need to repaint this place!

Oh yeah, that much lighter spot on the table top is evidence of my BIL's inability to pack a truck. Not on this trip, there was a different piece that suffered on this trip. A phd engineer and he doesn't even know about ratchet straps. Or cutting the rope/strap to useful lengths.... or a trucker's knot..... sigh. Oh well, still a nice guy, and within his specialty he knows a heck of a lot more than I ever will.

Also of interest, a failed pocket hole:

At first I thought this was a wane in the rail, but it had split the corner off, probably from whatever ham fisted packing job that also broke the table leg (it was right next to the broken leg).

All these holes for screws that hold the top on were clearly machine drilled, again likely with a dedicated set up machine that drilled a nice hole like this. I usually drill an oversized clearance hole, eyeballing from the edge of the rail, and then scoop out the pocket with a large, steeply swept gouge - good example of why I don't make stuff for a living, I want to have fun and have a somewhat odd view of what is fun 🤣

Awesome! I'd say you nailed the repair completely.