Trust in handling data doesn't really come into this; if anything Google has a very strong reputation for security.
Outcome is the same, but being "conservative" isn't the real reason.
Adding a vendor requires compliance work, process, finance etc that it's just effort.
99% of medium-large companies use Microsoft in some form so Azure can skip all of that to some extent.
That's not what the word conservative means, not by the dictionary or even politically.
Conservative is the averse to change or to hold traditional values without logic. It's more like a type of fear. Even if the change was easy or have 0 cost, a conservative entity won't do it.
In many cases, the conservative approach to a problem is prudent because the old ways work whereas there is more risk and uncertainty with new.
That's not fear, it's wisdom.