98 blazer engine not starting

I was driving when I lost oil pressure because of an oil line coming loose from the radiator, i was able to fix that problem but when i got back into the truck to start it ( a few hours later) I found that the batt. was drained... the flashers were not on and im not sure how it drained but i tried to jump it with another truck with no luck starting it... now what happened was that when i put the key in the cluster light up and the Security light was illuminated ( not sure what that is and if it matters) turning the key will get a "Click" out of the starter/engine like it wants to start but it doesnt... the serp. belt and fan move a little but it does not start and it does not click more than once... i even put it on a batt. charger for an hour with no luck and even resorted to a 100amp engine crank off the charger with no luck....

To be honest i know only a little about trucks, i can replace parts but im not good at diagnosing the problems... this is also my first time posting ...well... anything :)
I appreciate your help!

I'm a little nervous about "oil lines" coming loose.......they don't come loose......they leak, but they don't come loose......

You don't say anything about oil level or if the engine made a knocking noise.....any previous cranking problems?

First thing you want to do, is see if this engine rotates easily......put a socket on the crank bolt and see if the engine rotates easily.......

If OK, then the battery has to be checked......if ok, then you have to check the battery cable connections, to see if they are clean and tight and free of corrosion......if the battery is bad or the connections are corroded, you can jump the car until the cows come home and nothing is going to happen.....

If battery and cables are ok, then you check connections at the starter, and also check the purple wire to the starter for full battery voltage with the key in the crank position......if ok, and no crank, it's a starter....

ive been told that the plugs need to be out to try to rotate the engine?!

also, i assumed that even if the batt wad dead if i was getting a jump the other cars batt would supply power to my vehicle and it would run... point is my batt was bought 2 years ago with a used batt so your info was definitely helpful, ill try that

and the oil lines were loose because the tiny C clip that holds it into the radiator did not seet behind the flared end

Well the batt checks out okay,and I relized I have the remote start on my key fob.. I hit that while looking at the crank pully and the starter clicked like crazy and sounded like it wanted to advance the flywheel but it didn't budge.. I haven't gotten a socket on it to see if its seized so I guess I'm hopeing for a bad starter (I guess, lol)

Sounds like a bad starter after what you just said. With the chevy trucks you can smack it with a hammer or the end of a ratchet when you use the remote start and a lot of times it will make it engage. You don't need the spark plugs out. But you do need to remove the ignition coil wire before you try this or you can brake your arm or worse if it starts. It is the one wire on the rotor that does not go to a spark plug. You just need to turn it a little to see if it turns easy. He wanted to make sure it did not seize up the engine.