So now we all know Harrison Wells’ true identity. He told it to Cisco before he killed him on the episode “Out of Time”.
From the last episode, Tricksters, we saw what really happened to Harrison Wells 15 years ago. She had a wife named Tess and he is planning to build a particle accelerator and Eobard Thawne revealed it to him that it will be built on the year 2020. We also saw from the last episode what really happened the night when Nora Allen died. There we saw Barry Allen fighting Eobard Thawne who wants to kill the kid Barry Allen. Then Barry chases Eobard but Eobard suddenly lose his powers. Eobard then discovered that the speed force is gone and he cannot travel back to the future.
My theory is Barry disappeared because he is already in the Flaspoint Paradox and we all know that in the Flashpoint Barry do not have his powers. This is why Eobard can’t access the speed force anymore.
Eobard Thawne’s real plan is to kill the kid Barry Allen but he failed because of the Flash. He was then stucked in that timeline and Barry Allen really became the Flash by the year 2020 because of the particle accelerator. He then stalked Harrison Wells, the one who will create the particle accelerator and planned to absorbed him so that he will gain Harrison’s memory and appearance.
So why does he need to absorb Harrison Wells? It is because he do not have the knowledge to build the particle accelerator.
So why does he need to build the particle accelerator? It is because he need Barry Allen to become [The Flash](series:1068303) because Barry is the speed force and every step and run Barry makes the speed force grow. Without the speed force the speedsters will not have the ability to travel through time.
And now that he already built the particle accelerator and Barry Allen is already the Flash and the speed force is already back or accessible he is now in the move to train Barry to become faster and faster and one day he will absorb Barry’s speed that will lead to Barry’s death that we all know would not happen.
How do you know that he wants Barry’s speed? In episode 7, Power Outage, they encountered a metahuman named Farooq Griban aka Blackout who can harness electricity. He is also able to absorb or harness Barry’s electricity and Barry loses his ability to run fast. On the last part, Harrison/Eobard is seen on S.T.A.R. Labs metahuman prison on Blackout’s cell and says that he want to know how did Blackout got Barry Allen’s power. I think even with that device he used to the real Harrison he cannot absorb Barry’s speed. And all his plan was delayed because of the Flash present the night Nora Allen died.