Had some poplar milled from some large trees we had to take down here. Air dried in my shop for 4 years before having it made into a table. All it took was 1 winter and it split and bent severely inside the house. I will only kiln dry from now on.
I'm just speculating here but probably the support structure didn't allow for wood movement. You need something to keep the table top flat while allowing it to move. Screwing it to a stiff frame (steel or cross grain wodo) is certain to crack when the wood moves.
Breadboard ends, sliding dovetails or steel support with elongated holes (going to a threaded insert and bolt) are good ways to support a table top.
The wood was probably stabilized to your shop atmosphere but indoors in the dry winter, maybe with air conditioning or a fire place, and there's going to be movement.
Kiln drying does not stop seasonal wood movement.
If you share a picture we can take an educated guess what caused the table to warp and crack.
On flush, jointed boards, they are a permanent jig to hold the ends in vertical alignment. Imagine taping your fingers together to keep your fingers flat. Lateral movement is impossible because the boards are glued tightly together.
If you’re concerned about lateral movement then the more important concern is to have gaps between the boards. The bread board end is now a rail in which your boards can slide like wobbly carriages on a train track: aligned in one direction (up/down for a table) but with the ability to move independently in another (across the width of the table.)
Did you use a moisture meter?
The process is mostly: measure moisture content of wood, pick a humidity to maintain, check wood periodically to see if it is drying too fast or too slow. Weigh water coming out to monitor process.
Very low effort if you have space to allocate while in use. The wood came out well, no complaints.
One downside is you won't kill insects with heat, so you could have trouble if it is buggy wood.