The primary reason would probably be that Azure was the unproven new kid [1] on the block at the time these decisions were made at Snap. -- [1] Yes Google Com

The primary reason would probably be that Azure was the unproven new kid [1] on the block at the time these decisions were made at Snap. -- [1] Yes Google Compute Engine (GCE) is even newer than Azure, but Snapchat used (and probably still uses?) Google App Engine not GCE, which didn't even exist when Snapchat started.