The pressure to increase profits exists regardless of ownership, if anything having large institutional funds own the majority lessens the pressure (vs an activist fund or something similar). If they're leaving money on the table someone is going to take it.
Not really; you can look at BNSF (bought by Buffet) vs Union Pacific. Buffet takes the long view, as a result BNSF has been spending billions on capital projects and hiring.
Wall St is known for encouraging short-term thinking.
I'd say it's a lie that Wall Street is known for short term thinking. Hell, it is even a unofficial motto of Goldman Sachs to "be long-term greedy".
Are there a large number of activist investors who want certain companies to trim fat? Yes. I wouldn't always say that trimming fat is always synonymous with short term thinking. For all the companies that are underinvesting in the future, there are 5 whose management has given them mission creep to invest in areas that incinerate capital. Especially in the current interest rate environment.
BNSF is spending money on capex because it's the smart thing to do in that industry right now. That's not a consequence of a Buffet investment. Buffet also invested in Heinz and they immediately fired thousands and are cutting costs left and right.
