When I was a lifeguard in California in the 1970s, we had a saying: "You're safer if there's only one lifeguard around rather than several." When you're the only responsible authority on scene, you simply must take action -- you don't have anyone else to depend on.
In Uvalde, you had 376 responders from 20 different agencies, including 149 from the U.S. Border Patrol, 91 from the Texas Department of Public Safety, and 25 from the Uvalde Police Department. Who should have jumped in and taken initiative? The natural tendency of law enforcement is to default to the local agency, so it's a very difficult thing for any individual LEO to go past the chain of command. But in hindsight, we know this is exactly what should have happened. My guess is that if somebody had stepped up to the plate early on in the crisis and assumed an active leadership role, others would have followed him. In the end, however, nobody seemed willing to risk everything and do what they knew was right and follow the SOP for active shooters.
Safety in numbers? Sometimes there is and sometimes there isn't. More is not necessarily better.