When RT came out the world seemed like it was heading towards a mobile world. iPad sales were going up, and Microsoft was left behind again and again so they didn’t want to be left behind again. Did Microsoft believe that PCs are dying? Probably not, but that doesn’t mean they should just sit back and watch Apple grab all of the market share for ARM tablets.
The Pro wasn’t as thin and light as the Surface Pro 3 we have today. It was much thicker than the RT, and heavier. The RT existed as a mobile device that was cheaper, lighter and thinner than the Pro. However, it was dragged down by lacklustre performance, a confusing naming scheme (most normal people didn’t know Windows RT cannot run desktop Windows software), an OS with a split personality, and an ecosystem that never blossomed.
Of course, in hind sight everyone is going to say the RT was doomed to fail, but it wasn’t. It’s not like the is NO reason at all for a mobile tablet device to exist (look at the iPad), it’s just that Microsoft’s execution wasn’t good at all.