Firefox Crash Reporting - What?

[#1]

Just looking on my brothers PC where he mentioned that he often stopped a virus check because it took too long.
So I set Defender on a quick scan and the scan bar zipped along fast enough until near the end it seemed to come to a halt. A quick look showed that it was still checking thousands of files in one directory. The Firefox crash directory.
After looking in that folder I don't understand why there was so many files. Tens upon tens of thousands. Around 2.7GB's worth.
I've never seen Firefox crash on this PC so what was all those files in aid of?
I've deleted the files and turned off all reporting.

[#2]

Depending on the settings, Firefox collects how it's performing and some supposed anonymous useage. No idea what they're going to do with that data, putting on my sceptical hat I would say they're selling it for money. 

[#3]

It doesn't seem logical that those nearly 80000 files are really "crash" reports.
As the PC has been a running build less than a year if they were all really crashes.................................
His FF is a thirty something build.
Personally I still prefer an older version of Pale Moon.

[#4]

Well they're not crash reports as such, the telemetry data just happens to be stored there.

[#5]

I guess they must be.
I remember there was three tick boxes in that area with two of them ticked.
It's just so much though. 2.7GB is ridiculous.
Though I've not used this myself I assume those must be ticked by default.

[#6]

Your assumption is correct, they are indeed ticked by default. Although there is a small dialogue at first (or after installing the version that included it) but it's easy to miss or ignore.
It certainly is a stupid number, I'm not sure they do any automated cleaning of old records or it could have failed for some odd reason.