The somewhat befuddling increase in file-size has to do with the compression algorithm that is used to assemble the image-information into a a JPEG-file.
The algorithms can be different, although they all output in the same file-format.
A very simplified example of the compression can be illustrated thus:
BMP (non-compressed image format):
In a compressed format that can translate into
I.e. a notation that that specifies that the next 15 bits are all 0, next 12 bits are all 1 and next 15 bits are 0 again.
When you edit the image and save it again, the algorithm may choose to record notations about image-data that is no longer there. It's a "syntax" if you will for how the algorithm stores data about an image.
Gobbelygook yep..lol. You can - for example - convert a JPEG back to a BMP-image and it will become a bigger file - but there will not be more image data. Same principle.