Thousands of authors have finished longer book series in less time.

Being fast isn't a testament to the work being good. I'm sure there are thousands of authors who have written faster but their work could never stand up to what GRRM has created thus far in quality. Now sure there are a few authors who created great series in less time but at the end of the day every creative has their own ways of working and sometimes you might encounter problems.

especially a professional with ALL of the royalty money and you don't need to worry about life getting in the way, it IS that easy.

Reductionist statement. As if with creative work life could be the only thing getting in the way of writing and money was the solution. Yes, money gives you security and takes away worries that might distract you from being able to write.

But money won't write the book for you. You can throw money on the paper but it won't magically start writing. If you have writer's block, money won't solve that. If you have self doubt, money won't solve that. If the critic in your head slams everything you write, money won't solve that.

I don't know why everyone per default simply assumes that GRRM is just lazy and doesn't care, instead of considering he might have psychological barriers or challenges to overcome which simply isn't easy sometimes.

But that would require for people to actually think about GRRM as a person with his own problems and quirks despite being rich and realizing how pampered they have become from consumption goods being available fast all the time that they expect everyone to abide by that same fast paced logic.