User blog comment:Starcitiesfinest4/Reverse Flash/@comment-27700324-20161107015352/@comment-3221148-20161110192542

Gifist8, rewatch. Harry explains there, that the Speed Force protects speedsters from changes in timeline, allowing them to stay alive despite them getting possibly erased from existence. When Thawne traveled with Barry from 2000 to 2016, he was protected from the effect of Eddie's erasure, unlike Wellsobard, who somehow still existed and got erased.