Gonna try my best here:

Crowdstrike is an anti-virus program that everyone in the corporate world uses for their windows machines. They released a update that made the program fail badly enough that windows crashes. When it crashes like this, it tries to restart in case it fixes the issue, but here it doesn't, and computers get stuck in a loop of restarting.

Because anti-virus programs are there to prevent bad things from happening, you can't just automatically disable the program when it crashes. This means a lot of computers cannot start properly, which means you also cannot tell the computers to fix the problem remotely like you usually would.

The end result is a bunch of low level techs are spending their weekends manually going to each computer individually, and swapping out the bad update file so the computer can boot. It's a massive failure on crowdstrikes part, and a good reason you shouldn't outsource all your IT like people have been doing.