Probably they are trying to take control of Bitcoin.
Yes, i know it´s impossible... until the day they own it all...
I think Gates simply got irritated with the responses to his earlier opinion. He used to be ok with it but earlier this year said that BTC is bad because it enables criminals with new ways to trade drugs and such. People criticized him for this opinion and I'm sure he read those comments and got even more salty that the world not only doesn't react or support him, but laughs. He's becoming a grumpy old man.
What we should expect from an old man?
Mood swings,non-clear opinions which would change anytime depending on what would they read up and i wasnt really expecting this. Remember on days where he do praise or do give positive views/words with bitcoin and now early this year we do able to hear out negativity which the entire community would really oppose since we do really have hope on what bitcoin can really contribute of in near future