The answer was presented to us when Barry attempted to regain his speed and at the end of season two. When Barry attempted to get his speed back, the process caused him to be absorbed into the speed force. While there, he was trapped. His only chance to escape involved the existence of a doorway and an anchor to the world outside of the speed force. In order to interact with this anchor, he needed a source of power to create a doorway out of the speed force. That power source and doorway was provided by Cisco and the anchor Iris. That was what he used escape.
I know what you're thinking. In season 3 when Wally escaped the speed force, someone had to take his place. Well, Barry had already put a replacement in the speed force, his time remnant (a copy of himself). He went into the future (your future self) and grabbed a remnant to defeat Zoom. Team Flash watched as it all unfolded (you were all there when I got my powers). That remnant had a life in the future and had it ALL TAKEN FROM HIM by Barry. In order to keep this from happening again (we both cannot exist), Savitar decided to take away everything Barry had before killing him. Barry selfishly tossed his remnant like a lamb to slaughter to his death in order to defeat Zoom. The remnant (like the Reverse Flash's remnant) wants to live and create his own happy ending. He wanted to help Barry defeat Zoom but did not realize that he would be sacrificed for that to happen. In his eyes this action made Barry "The Big Baddy."
Here is even more proof! The time remnant (when he died) dissolved in the same manner Barry did. That's how he wound up in the speed force. He escaped the speed force in the same manner as Barry; the only difference was that his power source was the philosophers stone. His link to the outside world was anyone that held the stone. His doorway was created by Wally. HR will be spared because he wasn't a part of the team when the death of the remnant occurred. The remnant hates Barry, and he hates Team Flash even more for allowing him to be sacrificed while their Flash lived. He knew about all the Team Flash members because he probably inherited the original Flash's memories in the future. I'm convinced that the remnant draws power from the philosopher's stone just like Cobalt Blue did in the comics (blue lightning). The writers have plucked parts from the comic and utilized it brilliantly.
Malcolm Thawne is the twin brother of Barry Allen (aka the Flash/Barry's Remnant on the show) and an ancestor of Eobard Thawne (aka Professor Zoom). At the time of the twins' birth, the doctor delivering them had already accidentally killed the child of Charlene Thawne during delivery. To cover his mistake, the doctor gave one of the twins to the Thawnes as their own and told the Allens that their second son had been stillborn.
According to the context of the stories originating from another earth, raised by the Thawnes as a con artist, Malcolm learns of his brother by accident as an adult. He learns the full story by confronting his "parents" and the doctor who delivered him, killing the latter in a rage. His grandmother, seeing true potential in his passion, teaches him the family secret of controlling the "blue flame" (probably called the Philosophers Stone on tv). Eventually he crafts a blue gem to contain the flame. The creation is fueled by his rage and jealousy of his twin "stealing his life" and can siphon off the Flash's super speed.
His first confrontation with the Flash and Kid Flash results in the flame absorbing him. Emerging years later, he shifts his focus onto his brother's "legacy" since Barry Allen had died to stop the Anti-Monitor while he was in the flame. His plan spans from the present to near the end of the 30th century, targeting the Flashes of various eras in between. His plan is undone by Wally West who skirts the edge of the speed force while carrying the shards of the blue gem. The power pouring into the gem overloads and destroys it.
This ALL makes more than enough sense. Flash's remnant is the villain. The writers used comic book story lines from Cobalt Blue, Savitar and Godspeed to make him a more formidable enemy. No one would have seen this coming. Let me know what you think of this article. I know I hit the nail on the head.