ahrefs - An observation with backlinks (competitors)

Building websites, I am not new to... SEO in today's world, I am.....

Ok, sure I was hit by the 3rd round of Panda Etc.... and trying to recover. Maybe I'm slow on the uptake but tonight I ran my ste through 'ahrefs' and observe my link count is slowly rising AND my'Refering Donains' are rising, almost in parallel.

So, in my niche, I see those that once spent their life on page 2, 3, 5 6, suddenly rise to page #1

Ran them all through ahrefs and they ALL show this trend...

Backlinks... Well down (on the graph)
Refering Domains... Well up (on the graph)

Could someone please explain how this happens? I though obviousley refering domains could only rise as more backlinks were gained????

Thanks

I can see atleast one possible explanations and two questions

1) it hasent been updated fully


2) Does every link qualify as a backlink? does a redirection qualify as a link?

3) How does expired domains works?