[carlosjobim]

You're making it out to be a decision, but it's not. Creators can upload their content on several platforms and collect revenue from all.

[Mordisquitos]

In that case the effect on YouTube's bottom line would be even smaller, if any. Creators posting their videos on other platforms would have a negligible to no effect on YouTube, given that it would remain the default (read "only") video platform for the overwhelming majority of the viewing public. A creator announcing "You may also see my videos on DailyMotion/Vimeo/Twitch/PeerTube/wherever" would simply be irrelevant to their mass audience, who would react anywhere between "Ok, whatever" to "I don't know what that means, ignore".

[BuyMyBitcoins]

Just because they can collect revenue from other platforms doesn’t mean it will be sufficient or anywhere near what they were getting at YouTube.

[carlosjobim]

Of course not, but it is a hedge against any decrease in revenue from YouTube, as speculated here. A hedge that doesn't cost anything.

[fsflover]

The act of publishing on PeerTube together with Youtube (or even one day earlier!) can be a good protest already in itself.