Inevitability
by Kegler

The end of a famous quotation can be found somewhere in the completed diagram. Two of the diagram entries give the author's first and last names, and are clued with wordplay
only.   Each clue (including those for the author's names) contains a superfluous word, the first letters of which spell out an 11-word phrase describing the quotation fragment.

Inevitability grid

Across
1Trouble in old west African country (8)
6Strange - I drew nudes bizarrely (5)
10Be concerned lately about Democrat in core group (5)
12Santa's young helper nearly flew back (3)
13Principle seen tarnished in Trump reception (7)
15Mother's small, wiry body (4)
16Choppers, overtaking movie alien chasing its own reflection, finally triumph (5)
18Vocally gave permission for our group to produce tapes (7)
22The lady's father lacks pudgy hands (3)
23Odds and ends destroyed inside tee crate (8)
24Something that makes older, noisier gear shifts (4)
25Heathen with faltering heart test glass spectacles (11)
27Red's Rhythm & Blues Club holds second of singer auditions (4)
29Dude initially lassoing tether around palomino's head, and falling (8)
32Hopping amphibian left headless (3)
35Dazed TU alums examine pairs of dots? (7)
38Exotic tours get adventurer out of bed (5)
39Loading weapon externally on U-boat's deck (4)
41Hid tools in station lean-to (7)
42Snake nearly harms wild pig (3)
43Desires only women embracing love (5)
44Unlawfully takes back rusty bar perch (5)
45Direct line nearly severed (8)
Down
1Soprano Kathleen reasons around areas of conflict (13)
2Breathing spaces are between identical poles? (5)
3Debonair Charlie cut art, oddly, having a unified design (13)
4Mild balm: use rare albino shark tails (4)
5Easily, though not at first, suggest refinements (5)
6Reheat snow, per crazy, entertaining meteorologist (13)
7Comfortable shade tree in the middle of Selma (3)
8Save regret about extraordinary escape (6)
9Mix-up of the relay races, seeing dog tear frantically (13)
11Consumed last part of tasty pomegranate (3)
14Gnarled tree to be axed in France (4)
17Leaders of environmental activists identified tree swallow (3)
19Our gerbil has no desire (4)
20Exciting, like a beer isn't? (5)
21To start with, bankroll one needed not coming back; it changes hands at the races? (5)
26Biblical character sounds thoroughly capable (4)
28United Nations competition is hardly inappropriate (6)
30Expression of contempt for famous itinerant bear (4)
31Greek characters' star spectacularly rising (3)
33Wilted bloom tears apart (5)
34In sequel, lovers obviously quiet down (5)
36Disapproving sound for article missing from reporting assignment (3)
37Drop a long, lurid story (4)
40Sounds like a couple dances, also (3)

Solution