Blackstone Group Inc. became an investing powerhouse by making successful bets on undervalued companies. For the next leg of its expansion, the firm is focused on companies with large growth expectations. Even if it has to pay up for them. Since Jonathan Gray ended up becoming Blackstone’s day-to-day leader back in 2018, he has encouraged the heads of its businesses, who collectively manage $619 billion of assets, to develop large-picture convictions and invest in companies or assets that stand to benefit from those trends. The new approach has led the New York firm to plow billions into faster-growing companies-including in the technology sector-to which it previously paid less attention. It has taken Blackstone out of its traditional comfort zone of turning underperforming companies around through cost reductions and efficiency improvements-and juicing returns by employing sufficient helpings of borrowed money.