Yeah, Windows on ARM (WOA) is older than the iPad. 
First of all, Windows is an OS and the iPad is a device. Second of all, the iPad was said to have been in development for over a year before its release. It's not like on January 26th Apple decided to produce the iPad and announce it on the 27th...
You're making an apple to orange comparison. You're comparing the port of an OS to the release of a device?
An Apple to Apple comparison would be the port of Mac OS X to arm (known as iOS), which was completed on June 29th, 2007, 2.5 years before that picture you posted.
Now for the orange to orange comparison, Apple beat everyone to the market with a tablet in the form factor of the iPad. Windows 8 devices were destroyed and Android devices were hastily put together to try and bid for marketshare.