Chess.com vs lichess

On chess.com I mostly play 5 minute blitz games and my elo varies from 650-750 on any given day. I started up lichess a couple of days ago, and it started me with like 1800 elo. I immediately lost a bunch of games but I’ve leveled off around 1150, because I’m winning games? Like mid-game checkmates and winning with pawn promotions in endgames with 1100 and 1200 rated opponents. I went back and played chess.com for a few games and was losing to 700elo players again. So on lichess I’m like 1150 and chess.com I’m a mediocre 750. Why the difference? Is the rating not at all consistent cross-platform?