If you're riding 650b wheels, you almost certainly know what you're doing, but any mention of a "split seam" in a recently installed tube supposedly being responsible for failure of the tube raises a warning flag---especially with an oversized tube such as you were using. It's extremely easy to trap part of an oversized tube between the tire bead and the rim, leading to an eventual explosion, immediate or delayed.

After you install your next tube, inflate it to just a few pounds of pressure and then check around both sides of the rim. If and when you find a section where the tube is visible, pinched under the tire bead, work the tube back into the tire such that it is no longer visible. Once you're sure that the tube is entirely within the tire and not pinched under the bead at any point, inflate cautiously, 10 pounds at a time, checking after every round of inflation that the witness line above the tire bead is visible all the way around the wheel, without any high spots or low spots.

tl;dr: chances are that the tubes aren't defective; you might just need to be more careful installing them.