Big tech piles up large amounts of cash as it is and they have no idea what to do with it (other than shovel it back to shareholders). They have far beyond the margins they need to keep expanding, even with a 50% income tax. So the first thing it would do is cut into shareholder returns (less cash), their multiples would contract as investors would find them less appealing. Half of America is invested in big tech (in one form or another), and those are by far the most active voters. If they see their portfolios tank due to a huge hike in corporate income taxes, they'll promptly punish the politician/s that are responsible for it. Big tech would keep growing at 50%, so what's the alternative? 70%-80%? It's unlikely to ever have the support required to get it passed, it just plain sounds very egregious as a policy. At very high levels it comes across as: we like to punish success; and that's how it would be run against politically by the other side (Republicans).