Weellllll, if the cam was turning, your belt is probably OK. It could have jumped, but not likely. Has the belt ever been changed?

I am leaning towards no fuel or weak/bad spark.

Before this happened, was the Check Engine Light (CEL) on?

How many miles on the beast? Generally speaking...on a fuel injected motor, anywhere between 125k and 175k the fuel pump can go at any time. After that, tis just icing on the cake. You may have a removable, plate, in the floor, or bed that makes the job easy to do...if not, tis a pain, but doable (that said, never done it, watched it done is all).

Assuming that they are in the proper configuration, in order to run a motor needs: Spark (which you have), compression (which you probably have, as it is not likely that it disappeared on all 4 cyls at once), and gas (our top suspect).

Therefore, I'd put some gas, or starter fluid into the intake, TBI, or somewheres and see if it fires. It should fire for a second or two and then die.

IF it fires, then you know that you aren't getting gas. If it doesn't...either too much gas (not likely, but possible) or your spark is not strong enough or your spark is not at the correct time. This brings us back to a jumped timing belt, or some other reason that is just as mysterious.

You could do a fuel pressure check. W/o looking at your manual, It possibly should have 40-50#, maybe more. Anything over 25# and it should run...so-so. You probably have a wire somewhere, on your PU that you ground and it energizes the pump for pressure testing purposes and a spot, on your fuel rail to hook up a pressure gage.

You just changed the plugs, right? The old ones were wet, correct? If your plugs are wet, you could either have weak spark, or a rich mixture (but it should have been throwing a CEL code). If your motor is running rich, it WILL foul the plugs, regardless of the condition of the ignition system. It may take 10K miles to do it, but it will.

If it doesn't fire by inducing fuel into the manifold/tbi/etc then it has enough fuel. Especially if you have fuel fouled/wet plugs (that brings us back to Ignition. But, it also raises the possibility of too much fuel...not likely, but possible.

Take one of your old sparkplugs, put it in a wire and ground the plug, crank it. What is the spark, if any like? It should be blue, not yellow. Autozone has a tester gizmo, that you put in a sparkplug wire. It cost less than 10 bucks.. It has a screw, that you clip to a ground...you turn it out and it will show you how many volts are in your system.
Great Neck/Adjustable ignition spark tester (25069) | Ignition Tester | AutoZone.com
Anything over 20K is fine (actually enough to run on). 25K is common to many vehicles and 30-35K is what a stock Chevy HEI puts out and is one of the best out there (way more than enough).

Autozone has Codereaders....but you have to tow it down there. Once you get it running, you could drive it down there and have them read the codes.

Coils don't normally go bad (they do, but they normally last a long time). Something could have made your coil go bad.