Because starting on October 17th of this year, Harry will be running an antar (sub) dasha (time period) of a debilitated planet (Venus) until October 17, 2021.
In the fall of 2021 he will start his Rahu-Sun dasha. His Sun is his strongest planet since it is his atmakaraka, the Sun is in its own sign (Leo), and the Sun is in a nakshatra/lunar mansion that it rules (Uttara Phalguni). Also, his Rahu is placed in a nakshatra ruled by the Sun (Krittika).
I would just expect it to be a much better time period than the one he’s going to start soon.
House of Brat 