D30 axle u-joint questions

So, I was replacing the 760x u-joints today, which was my first time, using a u-joint tool from harbor freight. I was pressing in the last cap when then end of the opposite side cap when BANG!

1) What did I do wrong? My only thought is I tapped the cap in slightly crooked, and when I was pressing in the opposite side it pushed out the end of the cap.

2) Can bad wheel bearings cause premature u-joint failure? These 760s had less than 10k miles on them and had quite a bit of lateral slop.

Now I have to wait until Monday to pick up another u-joint to finish the install.

TIA

You may have had a needle pop out of place and get sandwiched in there, I use just a hammer and a vise to do mine. I was too eating u joints just on one side, turned out my steering stops were not properly adjusted allowing for too much steering angle for the u joint to handle.