Well Cap wasn't a SR stalker loser so that question is moot, lol.
Well since we were watching the timeline that did turn out to be the "1 in 14 million" then yes they were always destined to win. I guess you could say that Cap's time travel back to Peggy was an indication that they were always going to win but since we never realized that that even occurred until EG it was never a foregone conclusion for us the audience or Strange who never knew that the timeline he had grown up in featured two Captain Americas in his past.
Also since Steve only went back to Peggy after they beat Thanos and he didn't create an alternate timeline by marrying her then the "1 in 14 million" would have still been the one whether Cap went back or not. Meaning there could have been an original timeline that Cap tweaked but didn't create enough of a ripple to A. make an alternate timeline or B. screw up the 1 in 14 million (thank God for him, lol.)
However just as an FYI the writers and Russos have different takes on what Cap did. Writers say they always envisioned Peggy's kids being his but Joe Russo said in his mind Cap created an alternate timeline and then somehow crossed back into the first timeline to give the shield to Sam. So you can take whichever interpretation you prefer.