Daryl actually it is quite a rare occasion to see them in such numbers. First it is mostly upon season - winter time they tend to make groups - tho smaller - up to 15-20 maybe. However sometimes those groups coincide with each other and you may witness a display as above.
It should be noted that almost all those stags are young to middle aged (up to 8 years old). Old bulls (over 10 years old) tend to hang in smaller groups - usually 3-4 and you may take my word you won't see them flashing out in the open in the daylight hours.

I saw 3 of those "Old Dugga Boys" (sorry for expression that I borrowed from African terms - but they are just that) on my last day.

They passed nonchalantly by our empty vehicle and stood in the dense thicket some 30m away, when we spotted them.

Huge heavy long bodies, massive necks, heads held low, standing perfectly still...you tend to imagine the huge antlers they carry - untill there is a turn of the head - eish - like the whole tree moved - bright spikes so far and away from the head and so many of them supported by massive, hand thick, almost 5 feet long stems...yeah they do belong into one of the Categories of THE Hunting Species...

Here are a couple of trophies hanging in the Hunting Maison

This one was suppose to be hunted by ex-Yugoslav president Tito - never happened - somebody else shot it and it was a well kept secret for quite some time (245 CIC points) - free ranging, natural fed don't get any bigger (odd angle so - for comparison - length of the scull is app 40cm ~ 16 ""!:

Or this one - only pair of its antlers were found after Yugoslav war in those places - stag was never seen or shot (known to public):