IIRC, the reason that PATCO members were so easily replaced is that there were thousands of trained air traffic controllers in the military. They filled in (under orders, of course) until replacements could be trained. Also, let's not forget that in the case of the PATCO strike, the strikers were violating a Federal law which prohibited Federal employees from striking, and Reagan gave them two chances to return to work before they were fired.
I lived on the edge of IAH in those days and knew several of the controllers who struck. They could not believe that the public did not rise up and support them in their demands. However, that was 1981. The controller I knew best was making $35,000/yr--a very nice salary for those days. Even his mother would say he barely got out of high school, but AFAIK, he was a good controller.
Under their work rules at the time they struck, they had to be on-duty (at work) 8 hours/day, 5 days/week. But, they were only actually working at the control screens 4 hours/day. The other 4 hours they were on break. I don't know whether it was their contract or just the standard working conditions, but they would work one hour on the screens, then break for an hour, then work an hour on the screens.
Among other things they were demanding a 32-hour work week (in the 1 hour on, 1 hour off mode). Most of us poor schlubs were working at least 40 hours week for considerably less than $35,000/yr. There was not a giant upwelling of public support for the strikers. And, of course, let's not forget that the strike did cause some flight cancellations, etc. and when you inconvenience the American traveling public in any way, you've lost them.