LESS short-sighted?Quite so! I fear you overestimate biological evolution.
Imagine a market with the same kind of behaviors you describe, only a million times larger, and where not only do markets fixate on 3-month returns, but if any executive tries to do otherwise he isn't just fired but summarily executed along with all his senior staff as a lesson to others. Oh, and management at all levels make Dilbert look optimistic: no one actually even knows how to maximize 3-month returns, or how to do anything at all in particular; they just stick with what they're currently doing and sometimes randomly try new ideas (and if 3-month returns don't improve, even for unrelated reasons, everyone involved is also executed). Oh, and sometimes the government introduces arbitrary new regulatory schemes with no reason or warning, and any companies that (by means of trying random new ideas) don't find a way to make decent 3-month returns also have all their senior staff executed. New companies get started semi-regularly, but they're managed just as incoherently. And the system has been running that way for untold millennia.
That's evolution. A chronicle of blind stupidity and senseless mistakes, unfathomably vast, written in blood.
Makes our silly human affairs look positively cheery in comparison, doesn't it?