1) Snowden had already been charged at that point and was running from the law. Morales's plane was diverted because it was believed to be providing passage to a criminal. While I don't know what Snowden did was right or wrong, it is clear that Snowden broke laws. His intentions might have been good but he broke some very serious laws.
2) Roman Protasevich, on the other hand, is a blogger. He hasn't released any state secrets that he swore an oath to protect.