Huh? MBR to GPT- weird stuff

[Quietman]

So I have a Win10 disk I'd been wanting to convert to GPT and finally gave it a try after backing up. The boot disk was the only one left that was an MBR out of the 4 disks I have.

So I convert from MBR to GPT, and as I knew might happen, no boot. So I go and convert back to MBR, no boot.

Well time to do some extra work. But then I decided, "Oh what the heck". So I did the MBR to GPT conversion a second time . . . . and it boots with no issues.

So I sit there scratching my head thinking, "Well I'm definitely NOT going to complain, but what the heck just happened?"

Curious if anyone might have a thought on this.