I'm not so sure, you're comparing it only to C,C++ or Tcl/Tk but what about Ada? Smalltalk? Lisp? Objective-C?
Plus Java's standard library was full of bugs for a looonnng time: they focused on new features instead of fixing it.. I've experienced "Java can't print" myself while Java's hype was going full force..
Ada compilers were bloody expensive.
Modula-2, Delphi, VB, Oberon, Modula-3,..., were great, but they were either only available commercially, or OS specific.
Java was given away as free beer, with a batteries included standard library and with less hurdles than trying to write portable C or pre-C++98 across all platforms that existed in the 90's.
That alone made us try it out,
On my university, the computing department changed all the compiler design and distributed computing classes to Java, without Sun paying anything to a tiny Portuguese university.
But a well written java server-side application (so something that doesn't need to be started very often but generally just idles until it's contacted by clients) is as fast or faster than anything you were likely to be using for a couple decades after its introduction.
"were"? I don't know.
Smalltalk was neat, but never caught on, possibly due to the lack of free implementations and the difficulty of integrating with anything else. (The original prototype of the OS/2 3.0/Warp UI was done in Digi-something Smalltalk. (Waves feebly from IBM.))
Lisp, in particular Common Lisp, was very popular in certain areas, but again died out. Possibly another combination of lack of free implementations, integration difficulty, and sheer difference from the alternatives. (Scheme. Sigh. The cleanest language design ever. But no single OO design when that hype train was at full speed. Plus, parentheses, which well Common Lisp had already poisoned.)
Guy Steele said that Java dragged the industry halfway to Lisp, if that means anything.