Not only are there lots of tools to statically analyze C.

There are a number of tools to dynamically analyze C. For example tools that tracks the allocation of memory (or other resources), allowing memory leaks to be mapped back to the source line that did the allocation.

There are tools to document the source (like Doxygen).

There are editors that understands the syntax and can separate variables with same name in different scopes. Understanding C, they will not just manage auto-completion, but can do refactoring, where you may change the name of function parameter and the editor changes the name of all references to the parameter without touching a global variable with the same name.

There are large numbers of existing libraries to communicate with displays, or Modbus or traversing a file system.

There are tools that can (semi-)automatically generate test harnesses - extra helper functions used to exercise the individual functions in a C program.

Many of the above things can't be done with assembler because of the lack of structure, making it impossible for a computer to see all loops and make the correct assumptions about them. Many other languages can allow all of the above, but the availability is greatly affected by the number of users.