They basically mean that as a public company, Tesla often has to think about short term successes. Otherwise their stock price goes down and they get bad press and that can affect their business. Every quarter everyone worries about if Tesla is profiting or if they hit a delivery milestone or if everything is going perfectly. It's understandable, but ultimately, everything Tesla is really trying to do is longer term goals, where missing a deadline by a couple weeks/months isn't actually a huge deal in the grand scheme of things. Going private allows Tesla to not have to worry about any of those short term issues and just focus on the mid to long term goals they have. It allows them to better operate at their own pace and not be under as much public scrutiny.