Not sure if you're as naive as your comments here, or just spouting the standard jargon, but even "We're using most of the funds to develop our professional offering" and " Our investors leave free to work on whatever technology" are in complete disagreement. "They never interfere" - right... I don't doubt you strongly disagree, but history says you're wrong. Maybe Arduino will be the exception but I wouldn't bet on it. You took the money; you made the deal. If ever it comes to a decision that would negatively impact your investors or hold to the original ideals, which way do you think it will go?
That depends entirely on how much control the investors have. For a company as old and established as Arduino and for only $22 million, I’d guess it’s not all that much.