If you want to sell on premise enterprise software then Java is a big plus.

Also if you plan on exiting the company to a strategic buyer then your stack will come up in the due diligence and if it is a stack they are not familiar with then they can call off the deal. That is another, minor, reason why enterprise software companies chose Java.

But stacks are always a moving target. Todays hipster stack might be tomorrows mainstream. Postgres was an obscurity compared to MYSQL in the early 2010s and it has picked up tremendous stream since then.

And getting product market fit is more important than choosing the right stack. You can always use duct tape if you get lucky enough to have problems with scaling.