Was Microsoft to blame? No - the NSA.

[Geek-9pm]

According to Kaspersky Labs 98% of infected PC's were runnin Win7...

Yeah, that got noticed. They repeated the report from Kaspersky
https://www.reddit.com/r/windows/comments/6c5evh/almost_all_wannacry_victims_were_running_windows/

According to data released today by Kaspersky Lab, roughly 98 percent of the computers affected by the ransomware were running some version of Windows 7, with less than one in a thousand running Windows XP. 2008 R2 Server clients were also hit hard, making up just over 1 percent of infections.

Windows 7 is still by far the most common version of Windows, running on roughly four times as many computers as Windows 10 worldwide.

This would mean the talk about the XP issue was off base.
EDIT: I can not get to the source. Here is a link to the Verge, which has a graphic that appears to be from Kaspersky.
https://www.theverge.com/2017/5/19/15665488/wannacry-windows-7-version-xp-patched-victim-statistics