Suits like this often have narrow time windows of stock ownership to be eligible to participate in the suit. You can look up what the requirements are.
I haven't bothered to do that but it's a good bet most of the suit members have missed most of the gains in TSLA since the lows of 2019 and are hoping to profit a little bit off their history of TSLA ownership, after the fact, through this suit. The term "TSLA shareholders" in the context of this suit denotes historical TSLA shareholders, not necessarily current TSLA shareholders.