Microsoft's actually been in the geo API game for significantly longer, pre-Google Maps. MapPoint started as a desktop GIS product in 2000 that let businesses create desktop maps, and they've had an online API since 2002... it started as a SOAP API: https://news.microsoft.com/2002/04/10/microsoft-announces-ma...
But it was pre-AJAX so Google Maps stole much of their mindshare. And it's been renamed so many times that no one can keep track of it (MapPoint, Bing Maps/Live Maps/MSN Maps, Azure Maps). Though the pricing and documentation has consistently been reasonable.