The rumor mill for a while has been Boeing took a more innovative approach and Lockheed did a safe route. This is somewhat analogous to the ATF where NorthMD took the more radical route with the YF-23 and Lockheed took a more conservative route with the YF-22. This time, the more 'radical' design won. With the news a few weeks ago Lockheed's design had been rejected, that meant either restarting the whole effort (the 'cost effective' fighter) or accepting Boeing's risk.
I bet the pause was due to two things: one, ofc, the cost, and two, the lack of trust in Boeing to deliver on time.
Given boeing's recent track record, I am placing my bets on the F-47 has significant problems, delays and cost overruns.