Wheel Bearing

You sure it's the bearing smoking and not the brakes on the new assembly? They could have been over tightened.

Stuck brakes could overheat the whole drum including the bearings. Does the wheel turn freely?

Does the wheel have a lot of play when you push and pull on it with that side of the trailer lifted? If yes then you have a bad bearing.

If not and you have significant negative camber (top of wheel slanted inward) then most likely you do have a bent axle or spindle. Hit any curbs or big potholes? How much weight do you have on that axle?

Not likely though that a bent axle or spindle would destroy a bearing quickly like that. 0Was the spindle badly scored or damaged the first round? p

When I bought a couple of Lippert drum kits (brake issues in my case) the outer bearings were just loose in the box and none of the bearings were what I would call properly greased. I ended up cleaning up and repacking the bearings before I installed them.

By all means get a new dust cover too....

Unlikely but it is possible the bearing was set too tight, causing the wheel not to turn freely even though there would be no side to side endplay.  Proper bearing tightness is just enough to take the end play out and no more.

You could DIY it. It's not really a difficult install, but you can't rush it because the brakes and bearings need to be properly adjusted. After more than one similar frustrating experience with mechanics either doing a poor job or ripping me off I just plan on fixing anything short of a major trans or engine rebuild myself and carry a fairly hefty toolbox to do it with.

In your case I think you have more than just a bearing/brake problem. You are reporting a camber problem too, right? Top of wheel tilted in? Unless the bearings are totally destroyed causing the wheel to be floppy when jacked up you either have a bent spindle or a bent axle. Can you confirm?