Why are pushups so unbelievably difficult to do? Even Knee pushups are difficult.

Hey all, on my fourth week of lifting now. In my garage that is with my own equipment. Weight bench with spot racks, treadmill and boxing bag etc. Today for a change I decided after completing my weight sets I would try 3 sets of 6 knee pushups. For reference I am 25, 266lbs and 5 foot 10 so I am carrying a lot of mass. As a kid I was never strong but I could do pushups somewhat properly (age 13/14) but I can't believe how far I've fallen.

I was literally so uncomfortable even doing a single pushup. I couldn't get low enough to the ground, I could barely push myself back up and I didn't even bother with the third set. They truly are horrible to do, not even because of the fatigue of it. It's just so awkward doing them with how my body is shaped. All my fat is on my stomach and thighs and barely anywhere else, so it's like a weight is plastered to my abdomen pulling me down. Even on my knees it was barely doable.

Surely the answer cant just be "DO MORE". I did a brisk walk for half an hour on my treadmill today so I'm slowly implementing cardio stuff.