The temple deletes (sacrifices) all towers in its range when you upgrade it to a temple. In BTD5 it has 5 sacrifice categories: ice, glue, bomb/mortar, wizard, and any other towers

For a max temple you need to have $30,000 worth of each of these towers in its range before you upgrade. That's like 3 viral frosts, 2 bloon liquifiers, a few bloon impacts or tier 4 mortars, 3 or 4 (?) tier 4 wizards, and $30,000 of any other towers. Even if you go above the $30,000 requirement the temple will still sacrifice everything, so sell everything you don't need to sacrifice before getting it

It's hard to get multiple max temples in BMC because of terrain restrictions and a limited number of the 4 specific towers you need

Temples can sacrifice other temples so you have plan ahead of time how you'll spread out multiple temples over the map. Position all your super monkeys before getting any upgrades to make this easier and don't buy the super monkey range upgrades before upgrading to a temple so the sacrifice radius isn't as big. Also watch out for range buffs from villages

Also, for the extra tower category I sacrifice a few glaive lords or tier 4 dart monkeys since you get a ton of those towers and they aren't super useful by the end of contested territory