Only one ATC isn't the issue here.
The emergency vehicle was told to stop and did not. Even a dozen ATC wouldn't have helped in that case.
I read that the emergency vehicle may have weighed 60,000 lbs. It can't stop quickly any more than an airplane can.
There is no "the" issue in airline accidents. There are always multiple factors, and all of them had to happen in order for the accident to occur.
Understaffing is absolutely a factor. Had tower and ground not been combined, the erroneous clearance probably wouldn't have been issued.
The ARFF truck not complying with the stop instruction is absolutely a factor. Had they heard and complied, the accident wouldn't have happened.
And there are likely additional factors that will come out in the investigation.
I recommend reading some final aviation accident reports from the NTSB to learn more about how these investigations proceed and what kinds of conclusions and recommendations they include.